I just saw this today and it was really great, but I just have two little things that are irking me:
(I'll throw up spoilers here because while this mostly doesn't spoil the plot, it may spoil someone's first time watching it because their conceptions of the movie are going to be swayed)
First off is something not about the movie itself, but the marketing, the critics, and the viewers. It was marketed as a big mind-screw, so since the movie turned out good, the critics went along with it and said it was a big mind-screw, which then made people seeing the movie think it was going to be a big mind-screw so they started making up questions and skewing the facts the meet their interpretations, when really it was pretty straight forward until my second problem:
The whole "did the top fall over or did it keep going" thing at the end. It felt really tacked on and just there so even the people following along with the plot who didn't find anything all that confusing would be thrown a curveball. It really had no substance other than this purpose since it's the only real reason we have to question if what we see is really what's happening in-universe.
(now for real plot spoilers)
The whole top thing doesn't leave a whole lot to question anyways, just offers a few possible endings.
1. The top falls over, he's in his real reality, everything's good (the ending I prefer since it follows Dom's character better)
2. The top keeps going, Dom is in limbo and recreated the world so he'd see it as the reality he knew before going into the dreams. This is the end that my friends prefer since that makes the movie dark and edgey and profound... although it throws away Dom's character. For example, he could have at any time created a dream where he and Mal and the kids were all there and happy, or he could have stayed in limbo instead of convincing Mal to kill herself with him, or he could have looked at his kids' faces when he and Ariadne were limbo; Instead, he didn't want to live in a world that wasn't real and waited until he could make his way to go back to them in the real world.
All things aside, it was still a fantastic movie.