Watching Avatar is the same cathartic experience as going to a Trans-Siberian Orchestra. And the same downside - it makes all other concerts, or movies in this case, look bland by comparison. It's not about suspension of disbelief, it disbelief that the world you see so vividly and detailed before your eyes is not real. Unlike any other 3D movies I have seen before, the 3D is natural rather than forced. Depth perception is human equivalent rather than the forced things that jump at you. Every little thing is gorgeous and tell me if the forest at night doesn't give you goose bumps.
On the downside, I really have to question whether this movie will look good in plain ol' 2D when they release it on DVD & BR.