I loved this movie! I saw it with a friend last weekend and am going to see it a 2nd time with DH (who hasn't seen it) this weekend.
I do not believe the end is reality. My reasoning is that Dom reuniting with his children in that manner is based on the premise that he was charged with murder for his wife's suicide which led him to being on the run and separated from this children. While watching the suicide scene involving his wife (Mal), I was struck by how odd it was. For example, she was on a ledge in a building across from the building he entered - how does that make any sense? The room she was stepping out of was in disarray just like the room Dom entered - kind of like mirror imaging. My belief is that there is no way that scene was reality. I think they were dreaming at that time.
I am leaning towards the theory that Mal (Dom's wife) was correct in commiting suicide to get out of the dream state, and her goal is to try to get Dom to do the same. I believe that Dom is still in Limbo at the end of the movie.
I also don't think that the top differentiates between reality and dreaming as there was continued emphasis throughout the movie that each person has to have his/her own totem. The top was Mal's totem - what was Dom's?
I loved how this movie left me with so many questions. I've been thinking about it all week. I also loved the cinematography. It's worth the money to see it on the big screen IMHO.
I am looking forward to seeing it again to watch and listen to the first scene more closely. Also, there were many phrases that were repeated throughout the movie. It should be interesting to see if I come away with different conclusions after a second viewing.