I think Snow Leopard was a good spot, as the system was really starting to improve from both the user's and developer's sides. It had the system-wide UI consis

I think Snow Leopard was a good spot, as the system was really starting to improve from both the user's and developer's sides. It had the system-wide UI consistency of Leopard but the stability improvements from 10.6. And it's not that OS X hasn't gained some good features since. Once they got the bugs out a lot of the iOS integrations like Messages and even Notes aren't too bad anymore. The problem is, they keep adding half-baked things that don't change, and re-re-re-iterating on things that were perfectly fine to begin with (like Exposé from 10.3).