Have you tried Psyco in a wsgi application (custom, Pylons, Django...)?
What does your set up look like?
Did you get measurable results?
The question you should ask is not did you get measurable results, but does it make your site noticeably faster?  Most web applications are not CPU bound, so even if JIT makes them faster, you probably weren't fully utilizing your processor to begin with.
It has been a very long time since I played with psyco, but order to get measurable results I would have to simulate thousands of concurrent requests, an unrealistic situation for the average web site.
Keep in mind that psyco is not compatible with 64-bit python.  The average website doesn't need more than 4gb of ram, but think that ram is generally of more value than CPU cycles.
Does anyone have any feedback on using Psyco in a wsgi application?