General Use / Gaming = Windows Vista (Home Premium)
Media Editing (Not Flash) = Mac OS (I don't own one, but I've used them)
Older Systems = Xubuntu
Overall Favorite = Ubuntu/Fedora Core (With Compiz-Fusion)
User preference is Vista Ultimate at the moment. Trying to go from 32 to 64-bit though.
If your a linux fan, I like Fedora Core.
Though, I'm looking forward to gOS (Google Operating System).
I like the ones that has windows in them.
that one with a cool looking start menu and starts with a X