Saw it in 3d this morning. I was actually expecting the worst, because I get annoyed at hype and Cameron seemed pretty obnoxious in interviews I saw about this movie.

The CGI is indeed very good, and I suppose they managed to avoid the Uncanny Valley effect because of the Na'avi's inherent alien-ness. So no trouble with suspension of disbelief. The world was quite beautiful, and the wildlife nicely rendered. But I'm sorry, and this may be a personal failing, but I really did not get the whole "this is a living breathing ecosystem" vibe from this movie any more than I did from Ice Age 3. Which admittedly uses a real-ish ecosystem as its backdrop, but you get my point. So you have rhinoceroses and wild dogs and horses and pterodactyls (and big pterodactyls). I don't see the importance of knowing what the dogs eat or where the bugs nest or how the trees grow. They don't really elaborate on it in the movie, and I don't really care.
So sorry if I sound negative - I actually think the SFX are great, although on my part as long as you avoid the characters looking Final Fantasy - creepy, I'm happy. So I can't really tell if this is so much better.

My main problem is with the plot - this movie has basically been done before, multiple times. From Pocahontas to the Last Samurai with some Dances with Wolves mixed in, it is cliched beyond the point of cliche. At least the acting was good enough to make me buy it - which I suppose is a testament to the quality of the mo-cap CGI performances.

In the end I got a solid, action-packed, fun movie which I really enjoyed, and the 2h30+ length seemed to zip by. But it hardly reinvents the world of movies as we know it.