This is what I felt after watching the movie. Before interval it was gripping, promising and visually stunning. My assumption was 4.5/5. But the tempo could not sustain as the movie progress after interval. It suddenly changed the genre from fantasy and thriller to family and romance :) ... here the pace became slow. Again in last 15-20 min it revives some Cameron touch with some good action and visual effects.
Overall Cameron failed to generate the Titanic magic. But a new angle what I liked most in this movie is showing the link between all the lives in universe. The human communicating with the animals, birds and trees shown in a very beautiful way. I almost convinced myself to get converted to a Na'vi, join the local army and save Pandora. But the movie failed to reach the league of "Lord of the Rings" only because the emotions could not find a good, well built and gripping story around it. The feel good factor was not there at the end of the show.
Watch it once and forget, because everytime you can't watch it on 3D. Just an above average movie from the director of Titanic. 3/5