For all my applications, going to PyPy was an instant 2x improvement.

Not only that, it is a lot easier to hack on. I might be biased, but the whole implementstion idea of PyPy seems a lot more sane.

I think for pure python performance it is significantly faster at least on all the benchmarks I have seen. That said a lot of what people actually do in python calls into libraries that are written in C++ or C, which I believe has a similar performance (when it works) on pypy.

> when it works

This is the problem!

Yes it is.