I'm a big fan of the Finder of System 7. It seemed to hit the sweet spot where you could do just about everything you needed to easily (it had collapsible tree views, folders, computed folder sizes, drag & drop, copy & paste, labels, etc.), but it didn't try to hide things from you or restrict what you could do, it didn't get too fancy and guess at your common tasks, it actually showed your filesystem instead of Apple's prescribed guess at what your filesystem should do, and it was still simple enough that you could wrap your head around exactly how it worked.

There seems to be this phenomenom where good products seems to get better right up until they get mainstream adoption, and then they steadily get worse. It's like up till then you have room to improve, and then suddenly you've hit the pinnacle of product design in your category, but rather than hold it there, you have to make random changes so your employees have something to do and don't quit.

(To be fair, the one company that's tried the "great, let's make a great product, kill off the competition, and then hold it there and reassign all the people" was Microsoft with IE6, and that worked fine up until Firefox and Chrome came around and then completely screwed them over.)