This show is a fantastic show, and would recommend it to any cartoon fans. Thought not technically considered anime, it is really anime inspired (created by "nickelodeon" of course) and takes many themes from oriental traditions. For example, the actions for each type of bending (water, fire, air, and earth) are actually derived from actual types of martial arts (eg. Water bending greatly resembles martial Tai Chi). The art, backgrounds, scenes, etc. are all oriental inspired and the animators did an excellent job portraying it.
Aside from animation, the story line is very enthralling as well. A great storyline with very lovable characters. I download the show, and find that I have to watch 2 or 3 at a time to see what happens. The fight scenes are great, and like Iridis_vi mentioned, the atmosphere is very light-hearted, with very comical moments, but also very emotional as well.
As I already said, I recommend this cartoon to any cartoon/anime watcher. Don't let its creation by Nickelodeon fool you, it is a great show for children, adults, and those adults that act like children 😛