Some of the characters are pretty cardboard, and the theme doesn't really get to the depth it should. Also, calling it a low-gravity world doesn't excuse some of the world-building sins committed
But the graphics are truly amazing. It is seamless. Forget the wooden people in Beowulf or Zemeckis. The humans and tall aliens are somewhat segregated so you only get the sense of scale in a few scenes, but they work very well.
The other thing is that you sort of have to learn how to watch it. The camera presents different parts of the picture as in focus and you have to constantly shift where you are looking to follow the focus.
I wish I went to Up in the Air instead.
As to the ZOMG: Glengarry Glen Ross could have been filmed in the 1930s, but it's one of the best films in my lifetime. To say that Avatar changes movies forever is insane.