Back in the old days, there used to be a hardware property for the CD-ROM Drive that allowed you to disable "Auto-insert notification", meaning that it would not try to even detect when a CD had been inserted, let alone try to autorun it. This counted for music CDs as well as data CDs.

I can't seem to find that option any more... So now I just use tweakUI, like you said, to individually turn of data CD and audio CD autorun.