wxWindows hands down (Score 1)

In my mind, wxWindows is the best app framework out there. Uses C++ natively, but python bindings are available too. Supports everything you'd expect a modern app framework to have, plus a lot of extras people have added along the way. It's very similar in feel to MFC, with event tables and all, but the API is much cleaner, much more consistent. Best of all, it's cross platform: I can recompile and run my app without changing a line of code on Win32 and Linux, and there's Mac and Be ports on the way. The documentation is very complete and well organized (take that GTK), and my questions to the mailing list tend to be answered by one of the developers within a few minutes. It's distributed under a modified form of the L-GPL which allows you to build non-GPL applications using it, so long as you don't change any of the code in the library itself. Go to www.wxwindows.org and see for yourself.