but one of Apple's distinguished features was their high-quality icons

This was one of the things I loved when I switched to OS X in 2007. The Photo Booth, Pages, Preview, etc. were so beautiful. Also very easy to distinguish apps by icons. Now they all look the same-ish.

There was a lot more whimsy as well. The Adium instant messenger had its green bird logo as an icon. And the bird icon in the Dock flapped its wings when you had a new message (this was pre-native notifications, though Adium may have had Growl support already). I think it would also open its eyes when you started the app.