Overall, I enjoyed it. I successfully avoided the hype-machine on this one, which may have impacted my feelings towards it, but I can honestly say that I would have no problem recommending it to the average person.
Although the plot isn't going to win any awards for originality, (Dances with FernGully?), I do feel it was well executed as a whole. It tripped up here and there, both with length and the somewhat sporadic character development, but in the end I really did find myself caring for the characters, (or at least the idea behind them). If the topics within the story were featured in a larger number of mainstream films, I may have viewed it in a more negative light. As things stand, although far from original, the ideas presented are in no way common within the typical popcorn-flick.
Unfortunately, I was not able to see the film in 3D, (the nearest theater which I would've been able to do so is hours away from where I live). Every five or so minutes my immersion of the film was broken with the realization of how much more impressive the given scene would've been had I been watching it in the way the creators intended. Make no mistake, the movie is gorgeous even in 2D, but if you have access to a theater that supports digital 3D, I can only imagine that the film's world is well worth the ticket price based on the visuals alone. This is, after all, the movie that's been touted as a new benchmark in digital 3D since the very day it was announced.
This is by no means James Cameron's best work. Not by a long shot. It is, however, a damn good bit of fluff. I definitely recommend it. Just don't be expecting the next Citizen Kane.