Does PyPy work with NLTK?
I got a response via email (Seo, please feel free to respond here) that said:
The main issues are:
PyPy implements Python 2.5. This means adding "from future import with_statement" here and there, rewriting usages of property.setter, and fixing up new in 2.6 library calls like os.walk.
NLTK needs PyYAML. Simply symlinking (or copying) stuffs to pypy-1.4/site-packages work.
And:
Do you have NLTK running with PyPy, and if so are you seeing performance improvements?
Yes, and yes.
So apparently NLTK does run with PyPy and there are performance improvements.
Does PyPy work with NLTK, and if so, is there an appreciable performance improvement, say for the bayesian classifier? 
While we're at it, do any of the other python environments (shedskin, etc) offer better nlkt performance than cpython?