James Cameron is a friggin' genius.
At directing. At visualizing and getting his vision down on film or tape or disc, or whatever. At writing, nazzofastguido. But my sweet bleeding jeebus, that film is a visual freaking masterpiece. (As were Titanic and even Aliens.) My hat's off to him. And yes, I saw it in 3D, and I have to say that this is the FIRST film in which that gimmick wasn't a gimmick - it really added to the film.
Ignore the political message - you need to see this thing, and pay the extra for 3D.
Edited to add: In the sequel, directed by Paul Verhoeven, the "Star People" (dressed in leather trench coats and knee-boots, to the dulcet strains of Wagner) return to Pandora, drop tactical nukes from orbit as the ultimate in daisy-cutters, spray the 22nd Century's equivalent of Agent Orange on the rest of the planet, and strip mine the place for every picogram of "Unobtanium" ore they can get. In a fit of pique, Mother Pandora telepathically convinces the primary gas-giant to compress itself and ignite, thus wiping out all life on Pandora, including the hated "Star People."
There. I feel better now.