PyGTK are basically Python bindings for GTK+. Its basically C Gtk+ ported to Python, making it easier to use without removing any features. Most Python developers prefer wxPython (Python bindings for wxWidgets) or tkinter (default Python GUI Library, ported from Tcl/tk), but personally, I think pyGTK is way easier and more powerful. pyGTK not only offers superior widgets but also has pre-made widget containers in which you can just pack all your widgets. It is more object-oriented and needs less coding. The trump card of the GTK toolkit is the Glade UI designer in which you can design all the widgets and export them as an xml string which you can later use with your program.
For good pyGTK examples, head over to my project site: http://code.google.com/p/burningprodigytech