Re: But what about the GIL?
There isn't enough information for your comment to be useful.
Compared to what? CPython? Do you have benchmarks?
Edit: looking over the link above, it seems that for multi-microthreaded applications (like a raytrace or game application) PyPy is indeed worse. For tiny threads, I imagine the JIT compiler is giving a performance hit.
I also see that some frameworks like Django performs worse with PyPy.