Last night I saw Tron Legacy in IMAX and was pleasantly surprised.
Most everyone else has already commented on the look of the film (dazzling, if gloomy — is our own world gonna look this bleak soon?) and the Daft Punk score (downloading it from Amazon as we speak). I liked both, and the audience I was with clapped when Bangalter & Cie. appeared briefly in the club sequence.
The plot isn't groundbreaking, but there is a nice, heartfelt father-and-son story at the core — not just about the father inadvertently losing a son, but gaining another and being betrayed by him (although, in the father's mind, he was the traitor). That part of it, I think, will help it stand up when people come back to it later and some of the backlash/hype has burnt itself out.
Plus there are some intriguing elements about the presence or absence of a creator god, the spontaneous evolution of life, etc. — and while they're not developed as far as they could be, this is a Disney movie. I imagine they were not crazy or bold enough to give the helm to, say, Werner Herzog or Alejandro Jodorowsky and see what turned up. But oh man, just thinking about those ...
Re: 3D — I'm not a fan of it but it was used quite effectively in this picture, with only a couple moments of overload. The contrast between the movie itself and the overwhelmingly cardboard-y looking trailers — most of which I suspect were post-processed 3D — was pretty striking. But on the whole I'm more appreciative of flat IMAX or even classic 70mm than I am of 3D.