I tried updating my test.check version from 0.5.8 but now my tests run about five times slower.
Here's an initial rudimentary attempt to demonstrate that it's happening.
The problem seems to be one of my generators:
(def simple-map-gen (gen/map gen/keyword gen/int))
$ time lein with-profiles good test
lein test testcheckperf.core-test
{:test-var merge-count, :result true, :num-tests 100, :seed 1420337555809}
Ran 1 tests containing 1 assertions.
0 failures, 0 errors.
real 0m6.802s
user 0m12.791s
sys 0m0.615s
$ time lein with-profiles bad test
lein test testcheckperf.core-test
{:test-var merge-count, :result true, :num-tests 100, :seed 1420337628942}
Ran 1 tests containing 1 assertions.
0 failures, 0 errors.
real 0m29.254s
user 1m11.555s
sys 0m0.967s
$ time lein with-profiles still-bad test
lein test testcheckperf.core-test
{:test-var "merge-count", :result true, :num-tests 100, :seed 1420337718437}
Ran 1 tests containing 1 assertions.
0 failures, 0 errors.
real 0m30.646s
user 1m22.471s
sys 0m1.101s