My first 3D experience -- I loved it! It adds SO much realism! It took a few minutes before I was able to forget that I had the 3D glasses on, but after that, the movie was good enough--and exciting enough--that I was able to completely concentrate on the movie. My only real complaint about the 3D effect is that it does darken up the movie considerably.
I loved the closeness of the relationships between the characters in this one. All of the characters were so much more expressive than I remember from the other two movies.
Of course, the animation was awesome. Detailing on physical attributes is becoming SO intricate, as is facial expression and body language.