Don't know how I missed it, but Fredrik Lundh has been developing an extension framework for Python's built-in Tk based GUI toolkit. His module is named the Widget Construction Kit (WCK), and recently part of WCK's drawing mechanism has been implemented using aggdraw. In turn AGG is a high quality vector graphics library. Since Lundh is involved, WCK I'd bet the Python Imaging Library plays nicely as well.
The gist? Python is fast gaining an easily extensible, high quality, cross platform, interface toolkit. You don't just get a bunch of early 90's era widgets, but a framework for developing whizzy new interface elements. In Python no less!!