Yes, I left WoW last year, then came back for a bit for Cataclysm, then left for good.
I still think it's a great game, I just have played it a lot already, and it can no longer engage me as before. I did the whole raiding game in WotLK, and even if you have a pretty regular group of friends, it's still too much work and time to keep at it.
I have also done a lot of leveling/questing, and had enough of it. So I decided it was best to spend my gaming time playing different games instead of trying new classes or whatever. However, leveling up a worgen (up to 30s) in Cataclysm was really cool.