This is my opinon on the movie. Includes spoilers!
I knew before I have watched the movie, that most of subplots will be left out, since putting 20 episodes in 103 minit is not easy.
But the lack of details was still disappointing. (Especialy the part when Sokka, Katara and Aang come to Northern Water Tribe and Katara is not allowed to train waterbending with Aang and is instead forced to learn healing, which is important later on.)
Characters and their roles
I like how they catched the contradiction between Sokka (skeptic, pessimist) and Katara (optimist, always ready to belive).