I finally saw the film yesterday and enjoyed it a lot, partly because it is such an immersive experience.
A couple of flies in the ointment - firstly the bullshit hippy philosophy of the aliens, culled from shallow western interpretations of various cultures around the globe, with a dash of californication.
Secondly, the happy ending, which was expected, this being Hollywood, but unfortunately it completely undermines the rest of the film. Assuming it is meant to be an allegory of racist, rampant capitalism destroying traditional tribal cultures, we all know the real ending: the culture is destroyed by disease, murder, threats, theft of land etc, and those few remaining largely succumb to desperate poverty, alcoholism etc due to the loss of everything they hold dear.
The bogus happy ending wouldn't matter so much if it was just about the past, but of course it is still happening today (check out
http://www.survivalinternational.org/ if you don't generally follow the latest in cultural destruction and genocide) and what the happy ending says is, yes, capitalism is nasty but great courage and a nice philosophy can triumph in the end, so it's all okay. But great courage can't triumph in the end. It doesn't have the weaponry. Capitalism triumphs every time, and it is still happening today. Which makes the feel-good happy ending a little bit offensive really, even though I knew it was going to happen.
Still, a generally enjoyable experience until the stupid fightback of the tribes, and it was the first CGI-heavy film where I didn't get distracted by the CGI. Although it was still recognisable as CGI it seemed well integrated into the film. Overall quite an impressive achievement.