I would argue with your assertion that either TKinter of PyGTK are the best. There are several other good alternatives, including wxPython and PyQt, which are very comparable, if not better.
I would strongly suggest starting with PyQt. It's my personal favorite. I wrote a short tutorial on the Python Wiki. http://wiki.python.org/moin/JonathanGardnerPyQtTutorial I find that the Qt API is a lot simpler than the alternatives. Plus, it has great documentation. -- http://mail.python.org/mailman/listinfo/python-list
