imho PySide or PyQt is best. It it easier to learn and has an excellent drag n drop ui designer (qt designer). plus it has everything u'll ever need. u can write a complete gui app using only qt apis without any module from d standard lib. if u come from .net u'll find d api very similar. least i forget, it has excellent documentation too. checkout PySide on qt-project.org or PyQt on riverbankcomputing.com.

bb6xt, you use pyqt?

started out with pyqt4 but later ditched it for pyside because of the license. But both have the same api except for the initial import (from PyQt4 import QtCore or from PySide import QtCore). From the look of things pyside is not actively developed now so I'd advice pyqt, I hear qt5 is being ported to pyqt presently.

@webdezzi: I luv qt! I can use it in any language where it is support eg Python+PyQt/PySide, Java+QtJambi, C++Qt5 etc. However, I first discovered it in PyQt4.

I use pyQt too and since i've been programming, i've never seen a toolkit that makes life so easy as QT
it's GUI and threading are awesome. to have it go with python means you can develop great apps with one of the finest programming language.