Cameron's inventiveness is restricted to the production values which are very high indeed. Surprisingly, the story is often times quite conventional.
What really hurts is Cameron's returning to his love/hate view of the military, which goes back to the incompetent and cowardly marines in Aliens, and psychotic SEALs in Abyss. Ladle on heavy-handed updating of Vietnam combined with moralizing about Iraq and Afghanistan and you have a storyline which will divide audiences into supporters and detractors.
Antiwar movies like MASH and Apocalypse Now have attracted a wide range of viewers through subtlety and craft. In Avatar, we see craft on its own is insufficient to carry the story.
smashes the old saw about odd-numbered star treks being inferior.
Second, it's true they depart from the canon in some ways, but they explain the differences and are well aware of them. It's like the TNG episode "Yesterday's Enterprise".
this film is reminiscent of Wrath of Khan. Like TWOK, this is put together by a star trek "outsider" but one who knew how to make entertainment while paying homage to the franchise.
the actors are terrific, I especially like Krik and McCoy. They clearly spent time watching the original actors and their tics and do an admirable job alluding to them without parodying them. It's also wonderful to hear the "first time" the many star trekisms are uttered, "are you out of your vulcan mind" and so on.