I just started using PySide which is a Qt wrapper for Python. So far it's been very good. I chose it because I can get familiar with Qt and eventually I may use it in my C++ projects too.

I concur. PySide makes developement/prototyping really efficient : the code is easy to read, no build system to maintain, no heavy tools to run, portability makes life so much better, you can freeze applications => deployment is super easy (well provided you don't have to copy the file on every PC's of the customer :); can't beat the web for that). And plus, Qt is very old and thus mature. It may not be as fun as the web development (which I admit is funnier, at least for the GUI part) but it provides a solid, predictible framework... Now I admit, I didn't play with JQuery which looks very solid too...