According to this slide their "real world" tests of PyPy didn't live up to the benchmarks, and in fact showed "no clear improvement" compare with cpython http:

According to this slide their "real world" tests of PyPy didn't live up to the benchmarks, and in fact showed "no clear improvement" compare with cpython http://www.slideshare.net/KevinModzelewski/pyston-talk-111015 http://www.slideshare.net/KevinModzelewski/pyston-talk-11101...