I've been working with wxPython for a few years now and I like it quite a bit. The best thing about wxPython is that the UI feels native on the different platforms it runs on (excellent on Windows and Linux though not as good on OS/X).
The API lacks some consistency, but you quickly get used to it.
You can check out Testuff (shameless plug, as it's my own product) to get a feeling of what can be done with wxPython (although I must say, with quite a bit of effort).
