3D is not for everyone. First movie I watched my eyes were twitching for first minute after that I was fine. The quality is not perfect but definitely adds a different feel to a movie. Once more movies come out I think 3D will be better.
It depends on the 3D.
If its a fake 3D (Coraline, Clash of the Titans, etc) then its going to hurt your eyes.
If its a good 3D (IE Avatar) then its subtle and nicely enhances the movie without looking all cheesy.