I've had a surprising amount of fun with the game so far. It's not a great game, but it certainly isn't a bad game either. It's also very apparent that the game wasn't merely put together to cash in on the movie hype: there's a ton of content in the game and most of the time it looks absolutely stunning too (it's a pretty amazing sight when it gets dark for the first time and the whole jungle lights up like a christmas tree). If this is a 5.5, then FarCry 2 should have been a 4.5: both are similarly structured and both are guilty of the same game design missteps, but at least Avatar does have a somewhat cohesive narrative, a feeling that it gets harder and more intense toward the ending, a couple of fun vehicles/animals you can ride and it also changes up the scenery more often and more dramatically.
I'm absolutely pumped for the movie right now.