Until the material for the Summit PyQt presentation is ready, the quick'n'dirty way of doing it (on Diablo) is:

1. Clone to SD or internal card (you'll need the space)
2. enable extras-devel in the Application Manager if you haven't done so yet
3. (as root from console) apt-get install python2.5-qt4-gui

It'll pull in the python/qt4/pyqt dependencies and after a minute or two of munching, you're good to go !

PS. Be sure to check http://wiki.maemo.org/Qt for generic Qt on Maemo stuff, most of it is directly applicable to pyqt, too (except for scratchbox, which you don't need ).