Whether or not the film itself is racist, I think it was done intentionally to get people talking about racism and race issues, and in that regard it certainly has succeeded. While I was watching the film the impression I got from it was that this was almost like an apology to Native Americans for what America has done to their culture/race. Of course, if that was the intention it would have succeeded without the use of Jake Sully as a character, BUT despite the fact that he's white and becomes their saviour, his skin colour or race doesn't matter. His story is one about overcoming his own doubts/fears/emotions/prejudice. He learns about a different culture from his own and slowly embraces it. He then gives back to that culture by helping to rally them together against the threat to the planet. He doesn't singlehandedly save them - he only starts by putting the wheels in motion. I don't think he betrays his humanity in any fashion. He realizes that what the corporation is doing is morally wrong - just like how many other humans working for them do. He is just able to take more action against what is going on than those other people given his relationship with the Na'vi and his new found knowledge and experience.
I don't understand why so many are apparently offended by this story. We've seen the exact same thing dozens of times before and I don't remember people raging about it back then. Avatar copied from many different films. The influences from Dances with Wolves and even Dinotopia (lol) are extremely apparent.
I enjoyed the film for its stunning graphics, and I didn't mind the story, even though it was very obvious how the whole thing would end. The only thing that surprised me was Sigourney Weaver's death.