1) Full disclosure: I have not seen this movie. (If I do, at some point, it'll be because it literally looks good.) Despite this, I don't feel particularly bad about critiquing it. Given the number of reviews, the Wikipedia summaries, etc. that are available to me, I don't know that it's necessary to actually see the thing.
2) There's a pretty decent article here by Annalee Newitz that confirms up my concerns about the movie. In brief, it laments the sub-genre of films wherein a white guy - the Guy That (white, male) Viewers Can Relate To - is tasked with assimilation/eliminating an alien other, only to reverse course and join them. The link mentions Dances With Wolves, though Pocahontas and The Last Samurai also came to my mind immediately. Newitz also characterizes it as an expression of white guilt, about colonialism but also, I would imagine, about environmental damage. And in being an expression of guilt it's also, indirectly, an expression of an incredibly over-sized sense of self-worth and importance. (I'm thinking particularly, here, of Tom Cruise's character in The Last Samurai, who literally becomes the titular character and offers to teach the Japanese Emperor about samurai culture, as well as the guilt that the filmmakers are expressing for the industrialization and modernization of Japan, which serves to more subtly take credit for Japan's subsequent rise to international military and economic power.)
3) I find it impossible to remember what Sam Worthington looks like. To my mind, he has the most bland and unexceptional face I've ever seen on a celebrity, and he looks somehow like a different person every time I see him. (This, as opposed to my problem with Ed Burns, whose face I can remember but whose name I can never remember - and which I spent hours trying to recall when it first occurred to me that the problem I have with him is not unlike the one I have with Worthington. Also, I really can't stand Ed Burns.)