As a Mac OS X 10.x user, I'd have to say that the first two versions were pretty awful–but the subsequent releases have been substantially better, without, in most cases, huge driver re-writes (IEC 61883-6 / FireWire audio layers excepted) or a massive change in user interface.

Some might mistake this for a rip-off, but there is a bit of kaizen here–think of how much Microsoft stuffs into a Service Pack or Second Edition that could have been released out into the wild in a more timely fashion. Apple's point releases happen in a timely fashion and don't upset the apple cart tremendously.