To be honest, it wasn't the 3D that blew me away (although it was, easily, the best use I've ever seen), but the art direction...there really, truly isn't anything like Pandora, and the sheer amount of plant life and species shown was overwhelming. In fact, that's how my same friend described it as being! Although we did see a chase scene with an avatar being chased by a dragon-like creature (looked like the dinosaur that spits at you in Jurassic Park almost), which, of course, gave the 3D effects plenty to show off. Again though, nothing flying in your face or anything like that. Because Avatar is designed AROUND 3D, I don't think you'd want to see it any other way.
Again, the thing I get from this is simply how incredible the art direction is. My jaw literally dropped multiple times during the night scene. I can't stress that enough.