It's difficult to review this movie without separating the technological accomplishment from the rest of the movie. What James Cameron has accomplished is so visually stunning and viscerally breath-taking, that the rest of the movie is hard-pressed to keep up.
That aside, the movie is a pretty standard technology-is-evil-noble-savages-have-much-to-teach-us fare. Not that there's anything wrong with that...in many ways, a more complicated story would have distracted from the sheer visual spectacle. And it is a spectacle: an entire world as lush as the Amazon rain-forest, a cast more than half of whom are completely computer generated, and acting from the human actors that is seamless with there environment.