The open source Radeon driver also does a good job of avoiding tearing. I think there are some pathological cases where it can still occur, but it is pretty rare. Catalyst was terrible at avoiding tearing the last time I used it (getting on to be 3 years ago now). I haven't looked into it, but it is possible that the tearing issue may not be solvable without a KMS driver (i.e. no binary blob drivers can do it).

I used Wayland/Weston for a full work day about a year ago to try it out. It really was very nearly ready. I can't quite remember what problems I ran into, but I could do my work (as a web developer) with very few real problems. Probably it's time to look at it again.