Checked out a noon showing yesterday. Not really sure how I feel about it. It was basically Pocahontas 3000. Cameron could have titled it Pocahontas In Space and the movie would have made complete sense in that context.
Be prepared for a lot of very wooden, heavyhanded, poorly-written and poorly-delivered cheesy pedestrian dialogue. It also beats you over the head with the anti-imperialist, pro-environment themes and this really took me out of the film. The message is so heavy-handed it makes Michael Moore documentaries look fair and balanced.
That said, this movie is really only about the visual experience, but in that regard Cameron really hit it out of the park. The first hour is fantastic to look at, and the final battle more than makes up for the middle hour (which honestly kind of drags). Still, between the effects and the 3D it's really about as immersive as a film could possibly be. The talk of this "changing" filmmaking is mostly hyperbole though. Nobody is going to make a film like When Harry Met Sally or even a Bourne film using these techniques. It didn't change filmmaking, but it probably did change the summer blockbuster (which is not a bad thing). In the end, it isn't a very good "film" film and people aren't going to win screenplay awards for it, but it is a good sensory experience and worth the price of admission.
Plus the final action sequence was balls crazy.