The story turns "War of the World's" on its head by introducing humans as the aggressor on a peaceful planet and goes on to symbolize the director's distaste for military/industrial imperialism.
All questions, such as how a human can "drive" the body of an Avatar, or how the biology of planet Pandora "connects" all its living things, are abandoned due to the pace of the story and its stunning beauty.
I love how a man who has lost the use of his human legs goes on to become a warrior and hero, in some ways, a prophet or messiah to the Na'vi people. The sense of freedom this movie gave me is inspiring.