BTWTweak is a mod that is intended to improve Better Than Wolves mod experience.

Assuming BTWTweak v0.9o and Better Than Wolves 4.A9, (as of 25 Feb 2018) here is the list of changes.

When launching Minecraft:

(In some launchers may not work) a no-to-wolf icon for the program
BTW and BTWTweak versions displayed in the corner of the main menu
Controls configuration is now a scrollable list, and has a key binding for sprinting (default to Left Ctrl).
Easy difficulty is selectable again, but resets to normal after restarting the game.
Hardcore (permadeath) mode has optional hard difficulty, and normal otherwise.

In the early game:

Achievements are now technically possible in BTW. Ideally they need an overhaul but that's some future task.
Spruce and jungle trees are now easier to break. This makes softer tree types more suited for crafting, while harder ones are best left for fuel.
Tree trunk tops textures now correspond to the type of the tree instead of having oak texture, just like in later Minecraft versions. Stumps have correct textures as well.
The wooden and stone pickaxes last for 2 and 7 uses respectively, and don't immediately expire when you try to attack mobs with them. This makes starting (and restarting) just a little bit less tedious, and may prevent death when pickaxe is only weapon you have.
Stone and cobblestone breaks into loose rocks, which can be assembled together to make cobblestone slabs and cobblestone blocks. Stone tools are now made from loose rocks instead of cobblestone. This makes stone tools a bit cheaper, and the first furnace a bit more expensive to craft.
(Feature now in BTW) The furnace now shows whether it is full. Since ores take forever to smelt, you probably want lots of furnaces, and now you don't have to click every single one to figure out which one has contents.
When you dig gravel, sometimes you get a loose rock out of it. This makes shovel a viable choice for a first tool in order to get your first rocks.
Flints appear only rarely in place of rocks when digging gravel and stone. This makes flint more valuable.
Chests are now placeable next to each other, regardless of any adjacent double chests. Single chests will be merged to double chests as before. This allows configurations (especially together with hoppers) that were not possible before. Not being able to place a chest seemed like an arbitrary and awkward limitation. Placing a chest while sneaking allows to control which chest it combines with, or none at all.
Eating on the ladder is now dangerous. Don't try shooting with a bow or blocking with a sword while on the ladder either. It felt like an exploit that you could eat while climbing ladders.
Gloom has some nice visual effects, so you can be sure it's not that you go insane and beat yourself to death in complete darkness. It's something else.
If you die, a gravestone will be placed nearby, if possible. If you destroy it, you only get one rock. This is so you can have memories of your death if you manage to find your past gravestone. This can be disabled in BTWTweak.cfg.
If you play with "short" or "tiny" view distance, you will see the sun and the moon, since keeping track of time and moon phases are important parts of the gameplay. Fog distance has been pushed back like on "normal" view distance to let you see the ghasts that shoot at you in the nether.
Some convenience crafting recipes, like dirt/sand/gravel slab to piles, two cobblestone/stonebrick slabs to full blocks, book from cut tanned leather, grinding sandstone back to sand and concentrated hellfire back to dust.
A bunch of bugfixes. For example, you will no longer experience severe hunger loss while climbing a ladder. For a complete list of bug fixes, check the changelog.

A bit further to the game:

Seeds now root themselves when dropped on suitable ground. This makes some designs for farm automation possible in the mid game. Make sure not to lose your first elusive hemp seeds, though.
Chickens now drop one more feather on average. This helps reduce their amount (and the lag caused) when you decide to breed them for arrows.
Jack-o-lantern is now placed and dropped just like pumpkins, and if destroyed, attempts to place a torch. This is useful for lighting up ravines. Jack-o-lantern will go off underwater if facing water.
Ladder, wooden door, sign and sugar cane no longer stops lava, so do not attempt this if you were abusing this before.
It's now possible to jump out of boats and minecarts (and off pigs) without silly and somewhat unpredictable teleportation. This also could lead to interesting contraptions with jumping out of a speeding minecart.
If you are lucky and manage to find a witch hut (and loot it without dying), you can use the cistern you find in it to craft a cauldron. Just add a bucket of water and a bone on top.
Cauldron and crucible inventory has been reduced from 27 to 9 slots, and the interface now indicates if the fire underneath is stoked. If you want to process lots of items, you are encouraged to make automated builds that tilt the cauldron/crucible periodically with axle-supplied mechanical power.
Creepers are now hurt when deoystered. Not so stoic anymore!
Creeper hiss is now stopped immediately with killing or deoystering. Much more satisfying.
Hand crank bounding box has been lowered to avoid accidental clicking and to conform to the shape better.
Wearing boots now makes you walk faster, but added weight from heavy armor slows you down. Consider crafting boots first, it might help you escape death.
Snow blocks are no longer heat-resistant and will melt in warmer biomes under the sun or when placed close enough to any other light source.
Spider, enderman, zombie pigmen and blazes also have a chance to drop heads. Collect them all! Note that spider head is craftable to two spider eyes.
Renaming items is now possible again, thanks to the new Writing Table block. It is crafted with a piece of paper on top of planks. You can even create name tags with it to name entities. Named entities will not despawn. You will need Ink and Quill, crafted with glass bottle, feather and ink sac; paper, and 1 experience level to rename stuff / make name tags.
Name tags can also rename chests, furnaces, dispensers, brewing stands.
Written Book recipe was also changed to require Ink and Quill.
Ink and Quill can also be used to edit sign posts.
Fishing hook can now catch items and other entities it couldn't before.
Block of Padding now reduces fall damage, like a proper soft block.
Cows and sheep heal when they eat grass. Punch them to teach them a lesson every once in a while.
Silk, crafted from 9 string (and craftable back to string) can be used to store spider string in a more compact way.
Now beds are made with 3 silk on top of 3 padding on top of 3 wooden slabs and it's possible to use beds and lie down to rest, and regenerate even when hungry. Regeneration rate is doubled and hunger rate is halved when resting. Obviously, beds won't skip the night and won't set your spawn point anymore. They also work in other dimensions.
Diamond ingot recipe has been moved to the cauldron. Yep, this requires you to burn some wooden logs under the cauldron. This is more fitting for the now permanent nature of diamond ingots.
Logs destroyed by fire now drop ash. Also wither skeletons drop ash. It can be used as a fertilizer.
Wolves now respawn in forest biome (but not forest hills) like hostile mobs. This is mainly done to support long term servers, where no animals and wolves left for kilometers around. This can be disabled in BTWTweak.cfg.
(Feature now in BTW) Sitting wolf cubs no longer teleport to player as they grow up.
The void fog is gone. It was annoying.
Dynamite is now lit with hold and thrown with release of a button. This makes throwing dynamite more precise and much more fun! This feature is dedicated to the good old Blood 3D game.
Thrown rocks now destroy vases, and vases with blasting oil cause chain explosions.
Note blocks that stand on top of companion cubes will make bark sound. It is now possible to recreate Dogsong in Minecraft.

When you progress to the saw and tanned leather:

Better microblocks: it's now possible to fill blocks to the next appropriate shape by placing corners, mouldings and sidings: corners can combine into mouldings, mouldings can combine with sidings to become stairs or with stairs to become full blocks, sidings can combine into full blocks. Better yet, you can see where exactly your microblocks will go and if they get merged!
Sneaking now prevents falling from a rope. Rope climbing is much safer now.
Chest, gearbox, note block, jukebox, door, trapdoor, fence gate, pulley, bellows, ladder, bookshelf, hopper, platform, barrel, axle and saw, as well as decorative wooden blocks like pedestal, table, bench, column can be sawed with a bit of a loss. We all like recycling.
The saw won't touch pressure plate you put in front of it. It was strange when it made it pop out.
The saw won't break anymore when facing a wool block but will produce wool slabs.
(Feature now in BTW) Ladders are now placeable on vertically put sidings, or any suitable surface for that matter, not just full blocks.
Ladders try to place in the same orientation as a piece above it or below, if aiming at a side that cannot support ladder.
Torches, buttons, ladders are now placeable on backsides of stairs.
Buttons can now be placed on the top and bottom of the blocks. Unlike new versions of Minecraft, such buttons are symmetric. Also, the buttons are now placeable on any flat surface, not just full blocks.
Loose rocks can be launched with a dispenser or a sling. The sling is crafted with a piece of cut tanned leather and two ropes on sides. Note that the price for throwing rocks manually is hunger, and the arc they make is not really suitable against the Ghasts.
Thrown rocks will shatter glass blocks, or if something lands on them from a height.
The turntable doesn't only make smoke and clicks now, it spins visually!
Hardcore Packing with pistons now applies to loose rocks, which makes cobblestone, and ender pearls, which makes ender blocks.
New enchantment: Velocity. Applied to boots, and each level of it increases walking speed by 10%, up to 30%. Ocelots rarely drop Arcane Scrolls of Velocity, and also level 1 of that enchantment can be found in trades or made in vanilla enchanter.
Hard-boiled eggs can be made from raw eggs in a cauldron. Complementary to this, if you place an egg on a padding block with an active light block above, it will hatch. This allows you to control the end result of eggs precisely.
Storage blocks for Wheat, Diamond Ingot, Coal, Charcoal, Coal Dust, Nethercoal, Sugar, Bone, Nitre, Potash, Ash, Flour (requires 9 of each). All of them can be retrieved by crafting back to items. Block of Bone can be only crafted by Hardcore Packing.
(Feature now in BTW) Block of Flesh, squishy block made of 9 Rotten Flesh by Hardcore Packing and uncrafted by hand.
Block of Sawdust, made of 16 Sawdust by Hardcore Packing and uncrafted by saw.
Block of Slime, sticky transparent block made of 9 slimeballs. Note that it doesn't affect piston mechanics like it does in later versions of Minecraft.
Redstone and Lapis are now handled by Hardcore Packing, and all of the above storage blocks.
Small BTW fixes such as correct soap, rope, padding and wicker block hardness; Gloom now consumes player's meat, mycelium and huge mushroom blocks no longer show swirling True Sight particles, even though mobs cannot spawn on them.

When you get access to stoked fire:

Rails in abandoned mineshafts are rusted and won't give as much of iron anymore. If you need lots of iron, you need a mob trap.
On the other hand, ores are still relevant because cooking them in the Kiln doubles the nugget output.
Potash and ash can be used as a fertilizer for farmland or planter. It can simply be dropped on the top of the block, like bonemeal.
Stoked cauldron can make glue from 64 bone meal.
Wool blocks can be boiled in a stoked cauldron to retrieve components.
Piston can be melted down in a stoked crucible to retrieve metallic components. More recycling!
Charcoal texture has been backported the from newer Minecraft versions.
It is no longer possible to escape through the roof of Nether.

When you find a village:

(Similar feature now in BTW) Villagers now display newest offers in the beginning of the list rather than the end, to put an end to constant scrolling through offers.

Late game:

Cobblestone and stone drop in cobblestone blocks if destroyed by a soulforged tool. Like in good old times.
The effect of swiftness potion is restored. How to obtain it is left for the player to discover.

And finally, some general goodness:

Scoreboard sidebar is now shown only when player list (Tab) key is held.
Pressing Space (jump key) takes all items from a container. Complex slots such as crafting ones are untouched.
Pressing the hotbar key of already selected slot will cycle items in the corresponding inventory column. This is configurable in BTWTweak.cfg.
/playtime command that can be used to track the age of the world, and how long you've kept being alive.
New key shortcut, default on R, to open the chat with "/tell " + last told username so you can chat easily in private.
Sign posts now accept unicode characters.
Chat now accepts IME input and messages can be 256 characters long.
Improved font display for latin and cyrillic scripts when unicode font is chosen. That includes a fix for wider characters.
Removed the annoying inventory shift when player has effects/buffs. It was getting unbearable when running in and outside of a beacon range.
If you install over CraftGuide, it will be patched so it works from the inventory screen and compass and clock stop displaying real data in its GUI.
When disconnecting, the player entity is removed only after 60 ticks (3 seconds). This prevents exploiting initial invulnerability by repeatedly disconnecting and connecting in dangerous situations. Make sure to disconnect only when safe from now on.

Concerns, suggestions, feedback?

Go to the chat: http://chat.grompe.org.ru/#mcmoddev

Minecraft Forum discussion: http://www.minecraftforum.net/forums/mapping-and-modding/minecraft-mods/1290803-better-than-wolves-btwtweak-v0-9b-with-slings-and

Useful links

Changelog: https://raw.github.com/grompe/BTWTweak/master/patcher/readme.txt

MCP 7.51 download link: http://www.mediafire.com/download/95vlzp1a4n4wjqw/mcp751.zip

BTW download link: http://www.minecraftforum.net/forums/mapping-and-modding/minecraft-mods/1272992-btw (first MediaFire link in the post)

Minecraft 1.5.2 download link: http://s3.amazonaws.com/Minecraft.Download/versions/1.5.2/1.5.2.jar
Minecraft 1.5.2 server download link: http://s3.amazonaws.com/Minecraft.Download/versions/1.5.2/minecraft_server.1.5.2.jar

Libraries download links:
https://libraries.minecraft.net/net/java/jinput/jinput/2.0.5/jinput-2.0.5.jar
https://libraries.minecraft.net/org/lwjgl/lwjgl/lwjgl/2.9.1/lwjgl-2.9.1.jar
https://libraries.minecraft.net/org/lwjgl/lwjgl/lwjgl_util/2.9.1/lwjgl_util-2.9.1.jar

Natives for Windows:
https://libraries.minecraft.net/net/java/jinput/jinput-platform/2.0.5/jinput-platform-2.0.5-natives-windows.jar
https://libraries.minecraft.net/org/lwjgl/lwjgl/lwjgl-platform/2.9.1/lwjgl-platform-2.9.1-natives-windows.jar

Natives for Linux:
https://libraries.minecraft.net/net/java/jinput/jinput-platform/2.0.5/jinput-platform-2.0.5-natives-linux.jar
https://libraries.minecraft.net/org/lwjgl/lwjgl/lwjgl-platform/2.9.1/lwjgl-platform-2.9.1-natives-linux.jar

Natives for OS X:
https://libraries.minecraft.net/net/java/jinput/jinput-platform/2.0.5/jinput-platform-2.0.5-natives-osx.jar
https://libraries.minecraft.net/org/lwjgl/lwjgl/lwjgl-platform/2.9.1/lwjgl-platform-2.9.1-natives-osx.jar

Source installation instructions

Unpack MCP 7.51
Install BTW into 1.5.2 minecraft.jar
Place minecraft.jar, jinput.jar, lwjgl.jar, lwjgl_util.jar into ./jars/bin/ directory, and natives (.dll or .so or .jnilib files) into ./jars/bin/natives/ directory
Decompile with MCP, it will complain a bit
Apply MCP fix patch using the mcp_fix.diff file: patch -p 1 -i mcp_fix.diff If you have trouble with patch.exe crashing on Windows, use the one from Git distribution or make changes by hand.
Run MCP updatemd5
backup the ./temp/client.md5 file
Run MCP cleanup
Run BTWTweak.jar to patch minecraft.jar with BTW
Decompile with MCP again
Apply MCP fix again
put back the saved ./temp/client.md5 file
If working with BTW version BTW v4.AAAAAAAAAAHHHH or newer, delete dummy ./tweakres/FC*.* files
Copy ./tweakres/*.* directory contents to your ./bin/minecraft/ directory
Copy ./tweaksrc/*.java files to your ./src/minecraft/net/minecraft/src/ directory

Now you can modify source, MCP recompile and play using MCP startclient!

Binary installation instruction

Follow the Source installation instructions
MCP recompile, then MCP reobfuscate
Insert all ./reobf/minecraft/GPE*.class files into patcher/GPEBTWTweak_files.zip
If you added/modified textures, put them back to ./tweakres/ directory
Insert all ./tweakres/*.* files into patcher/GPEBTWTweak_files.zip
Compile the patcher if you haven't yet: "javac BTWTweaker.java CliPatcher.java"
Repackage the patcher: "jar cvfe BTWTweak.jar CliPatcher *"

Now you have BTWTweak.jar!