My initial worry was that they'd try to be too conceptual with the dream vs. reality scenario. Turns out they played with it just enough to be interesting, but not to be confusing. It was very clear and well planned; great visuals and "reveals." Some movies over 2 hours feel like they go on forever. This one didn't---once the end rolled around we didn't feel like we were sitting forever and we didn't feel like it was too long. An excellent balance.
Regarding the IMAX version, it wasn't true IMAX. Granted, it's great to see something big, but I kept waiting for it to go from widescreen to full side-to-side and top-to-bottom IMAX...but it never did. So we payed for IMAX, it wasn't true IMAX, but it looked great.
I feel neutral about what I saw; nothing much to complain about but nothing much to rave about. I could take it or leave it. It's not bad but it's not fantastic either.
Nothing really stood out to me. So many Hollywood movies are incredibly well-done but just "eh" in substance/plot/predictability/acting/etc. Thanks to computer graphics, this film is beautiful to look at and has a great sound track & sound effects; it's very well done. But besides great production (which is pretty common these days), it's only mediocre.
So: if you are attached to the comic or you just really want to see it, then by all means go see it. If you don't have a huge urge to go, then don't. I wouldn't go out of my way to see it.