Though the plot was predictable, the visual effects, beauty everywhere, and the sheer simplicity of this new world made the movie quite engrossing--made you forget the overgrown world we live in for a bit. One of the first movies in a LONG time where I didn't have a bathroom break!!! And it was a LONG movie!
Seeing in IMAX 3D was likely not necessary to enjoy it, as the glasses were pretty huge and sat on the tip of your nose.