I went to Avatar with pretty low expectations. What I saw of the characters in promos did not impress me much.
However, I was AMAZED by the incredible visuals -- and the 3D was breathtaking! If you can't see this in 3D for whatever reason -- wait until you can.
The story was engaging (you can't go wrong with "The Hero's Quest" -- Joseph Campbell proved correct once again). The characters were also very well developed and the computer graphics so well done that I forgot that these weren't "real" actors on screen. It's amazing how far technical capabilities have come in the last 20 years.