For a start, ignore Amazons description of the game (which seems to have been taken directly from the xbox/ps3 release). This is not an impressive 3D open-world battle for Pandora where you can choose sides and control vehicles; this is a very bad 3rd person stealth game. I feel like I could rant about this for pages and pages, but I will try to be concise:
Linear gameplay - You are supposed to be in a jungle, but you are basically running down green corridors. Some gaps can be jumped, some obstacles can be climbed over and some cannot. It all depends on where the game wants you to go.
Frustrating control - Your character moves at running speed, unless you are near an enemy, then he automatically changes to a slow crouching stalk. This often makes running up behind a guard before he turns around impossible.
No camera angle control - The left shoulder button zeroes the camera or locks onto an enemy (notice I didn't say "the nearest enemy"). If you are crouched behind a crate waiting to pounce on a guard, the camera tends to zoom onto the back of your head. Completely useless for stealth takedowns.
Derivative gameplay - No new ideas here, a bit from MGS, a bit from Manhunt 2, a bit from God of War. This wouldn't be a bad thing if Avatar did it better.
Repetitive gameplay - Run through the forest (i.e. down a green corridor), get to a landing pad/base, watch the guards set movement patterns, avoid the laser beams, mess it up because the camera angle makes it impossible, repeat. Even the flight sections don't save the game as you don't control where you fly. It sends you on a set course and you dodge or shoot mines.
No atmosphere - At no point do I feel like I am controlling a Na'avi warrior on the stunning planet of Pandora. This game completely fails to capture any of the majesty and wonder of the film.
In conclusion: Do not make the mistake I made in buying this game for the PSP, it has no redeeming features. You don't even have to take my word for it, check out some of the reviews on well-known online game sites before you purchase (like I should have done).