I used to have Extras as the default, enabling Testing and or Devel only when necessary. I know it is bad policy, but lately, I've had Devel enabled as the default, mainly because it's pretty rare at this point for updates to the applications that I use to be pushed to Testing, let alone regular Extras. (However, I will download from the Testing repo in order to vote for updates to the applications that I use)
sudo gainroot apt-get install python-pyside.qtcore python-pyside.qtgui python-pyside.qtnetwork python-pyside.qtwebkit python-qt4-webkit