It's fair to say this was the most hyped movie of recent times, but it fails to live up to expectations of being the best movie ever. The story is extremely cliched and predictable (think Dances with Wolves plus Fern Gully), and the 3D can be disorienting in some scenes where the little 3D objects distract you from the now out-of-focus action, and fast-moving action scenes are just dizzying.
That all said, it was still a solid movie. The actors were great and the CGI was absolutely breathtaking. The vistas of Pandora are so beautifully rendered, it's quite easy to see why this cost so much.
Short version: bad story, cinematographic glitches here and there, but recommended anyway because it's a new kind of spectacle.