Possible problem with the movie...
Is that there are no human characters. At least in the trailers, posters etc. suggest that. The first one was grounded in "reality" because of the human cast, and some practical environment. If there are no humans, and it takes place solely on Pandora, it's much more like an animated feature.
Also I don't know much about the transitions of some ofthe original cast from human to Navi, but it is confusing too.
(I guess there are some humans in the distance in the trailer, but they seem to be CGI too.)