Well, I've seen the movie yesterday and my take is: I don't care if the story has been done before, because the execution rocks the synapses like a trip through SkyNet's chronoport machine.
Visually it's stunning - reminded me a bit of the planet Na Pali from the game
Unreal - and the experience made me feel a bit like the first time I saw
Star Wars: as if the director was grabbing me by the back of my neck, throwing me down a deep pit filled with fantastic stuff, then punched me in the nose while screaming "yo, who's number one? WHO'S NUMBER ONE?" into my ears.
I really don't see where the whole "anti-American, anti-militaristic, anti-technology" stuff comes from. The hero and many of the "good" characters are American, and the protagonist is clearly a soldier who identifies deeply with the Marine Corps' creed. The antagonists are clearly hired guns with little respect for dress code, and the main antagonist is corporate greed (as in
Aliens). Even the Big Bad with a military background is so badass to be almost admirable in a twisted way.
The technology is not an enemy either, because without the Avatar tech the Na'Vi wouldn't have Jack Sully on their part and that would have been
bad. Rather, tech is neutral in Cameron's movies: like the Terminators, it can be used for good and bad purposes.
Ultimately, it's down to choices: Sully was meant to provide info on the Na'Vi, and at one point he decides to provide them
to the Na'Vi along with his experience. I think everyone can at one point identify with the Na'Vi (in our history we've all been repressed by some superior foe, more or less, and then kicked him into the nether regions with a vengeance).
The underlying morale (which I approve of, incidentally) seems to be:
there ain't no problem on this world or anywhere else that cannot be solved by the massive and deliberate use of guns, explosives and wholesale violence.