I can't say off of a benchmark but comments affect parsing. If pyc (or even better?) pyo files are already generated, stored, and run then comments shouldn't matter.

GCDialer (old name for Dialcentral) use to remove extra whitespace and merge multiple python files into one. I didn't feel the cost/benefit was worth it but didn't benchmark it.

I did do some benchmarking and found that class assignments are slow. When creating a lot of class variables (like pre-compiling a bunch of regexes) it was faster to create them on the instance. I normally have only one instance so no extra copies to worry about.

For general python optimizations there is already a decent guide
http://wiki.python.org/moin/PythonSpeed/PerformanceTips

Benchmarks are so-so for now but they haven't gotten a chance yet to do the optimizations they wanted. The real killer is this is very memory intensive which the acceptance into CPython is conditioned on improving memory usage. Start time is also an issue for now.

http://www.python.org/dev/peps/pep-3146/

Long term, PyPy is the project I'm more excited about. They've recently added support for CPython extension modules which was a major blocker for transitioning. Speed is a mixed bag. I'm unsure about start time or memory usage though.

http://speed.pypy.org/overview/