You can tell how many resources went into this serie, the world feels better than ever lively well designed, you can feel the culture of the air nomads and south pole perfectly represented by the environment and clothing.
The pacing is a little weird sometimes, specially at the most crucial scene when Ang takes his decition, it felt rushed and not natural at all.
The only big problem in the serie is the main cast:
Sokka is the strong point here, they made him a little more serious but it works specially well, and the actor not only look similar, his emotions can follow his words, perfectly portrayed.
Unfortunatelly (and having watched other eps as well) Katara is a dead character, the serie could have done well without her, you don't see emotions in that face, The very first time Sokka said "don't be angry" i was laughin because you could see no anger at all. She doesn't show her personality at all. And the script doesn't help either, Katara was a symbol of how women could be as strong as man, and they didn't use a single dialog related to that.
Aang actor also fails into deliver deep sadness, but he does very well with happy emotions.
Overall feeling is: this is worth watching, its way better than expected and a huge improvement from the old movie. I just hope i can see the actors growing with their characters as the serie progress.