Oh, oh, OS/2 was soooo nice! But as far as the best OS goes, I just LOVE BeOS. Shame they got bought up by Palm recently (but I'm still hoping that they will continue to work on it).
Be doesn't see as much support as other more known OSes, but it's fast, it's pretty much as crashsafe as any other POSIX OS, and it's easy to use even for newbies.
I guess OS/2 Warp would come second, but only by a small margin.
