I first saw it on a friend's PowerMac 7100, tabbed finder windows were great, where are they now? (here for $15.95, but that wasn't my point).

I didn't get it myself until the iMac, that came with 8.5. The new interface looked so modern, however now I think I prefer the way System 7 looked.
_________________
So this is how PowerPC dies... with thunderous applause