Do you recall what didn't work? So far web.py looks like a really nice rest-ful api backed framework. I rather like it.
At the time (and I have to admit my memory is a little foggy as it was 7 years ago), I believe we mostly switched away from it for maintainability reasons. It wasn't under active development, and we were in the middle of a complete MVC rewrite to impose some order on some otherwise organically grown code.
That's a little glib, but basically I ask other people with experience. You can throw as much fake traffic as you want at a framework but there is nothing like a real world test.