There's already Spyder, so I'm not sure how much value that would add. Plus, Spyder is still fairly new, so it's probably easy to find things to do there: http://code.google.com/p/spyderlib/wiki/NoteForContributors

There's also the Python plugin for KDevelop, which probably offers the most sophisticated semantic support for the language today, now beating Wing and MS in its level of type inference abilities, type tracking through containers, etc. So yes, a Python IDE using Qt is nothing new. But IDLE is simple and bundled with Python, so it serves a special role. I see it more as a teaching tool than a production-grade environment. It's just that having to work with the crummy Tk toolkit when hacking on it is a major turn-off.