hard one. Hmmmm...
Currently I use Workbench3.9, in lack of a better choise.
There just are no other operating system with support for the stuff I use for my music (recording, midi, multiformat playback, tracking, etc), except maybe Linux. Also, I play a few FPS, RTS, TBS, RPG, PFG, and other games that just don't exist on other inferior OSes.
