Btw, although overly simple (single CPU system!), this benchmark is
pretty interesting:

http://muharem.wordpress.com/2007/07/31/erlang-vs-stackless- python-a-first-benchmark/


About the GIL:

I think I've heard Guido say the last attempt at removing the Global
Interpreter Lock (GIL) resulted in a Python that was much slower...
which kind-of beats the purpose. I don't think it's feasible to
remove the GIL in CPython; the best hope of a GIL-free Python might
be PyPy.

The general trend seems to be that it's hard enough to program single-
thread programs correctly, adding to that extreme concurrency
awareness as required when you're programming with threads means it's
practically impossible for most programmers to get the programs
right. The shared-nothing model seems to be a very workable way to
scale for many programs (at least web apps/services).