I'm not as concerned about the aesthetics, although actually I welcome seeing some changes.
As for bugginess, Mavericks (after a few point updates) is decent. Mountain Lion is also pretty good, for the most part.
I have not been as impressed with Lion though. It really felt like a Mountain Lion beta to me, and the unfortunate part is that you can't upgrade from Lion to Mountain Lion on older machines, and at least 10.7 Lion is required for some Apple software, even though 10.6 Snow Leopard is less buggy IMO. The one that irritates me in Lion the most is that my dock disappears and I sometimes have to log out and back in to get it back. This didn't happen on 10.6 on the same machine, and it doesn't happen in 10.8 or 10.9 on other machines.