My g/f got me a DVD of Avatar, so I finally got to see it. Even without 3D, it's a good movie, though after reading the original script I think it would been a better movie if there was a little more backstory.
The latest IMDB review complains that it's a ripoff of Star Wars, which it is not. If anything, it's “inspired” by a Harry Harrison novel from the 1960's, Deathworld. That novel featured human colonists fighting the ecology of a planet that was all linked together in an empathic gestalt, so that the harder they fought, the meaner and tougher the hostile critters got. Admittedly the colonists weren't servants of a greedy megacorporation; they were simply annoyed at the small hazards of country life when they first landed, such as bug bites and plants with thorns. They got mad...and the ecology responded to their anger, starting the cycle. I'll bet James Cameron has read that novel.
Another possible source of inspiration is Alan Dean Foster's Midworld, which features human colonists who've gone “native” and fight to defend their home tree.
James Cameron is probably going to do at least one sequel, but first will come (I really hope this time) Battle Angel.