I used to think the end was reality for several reasons like hes not wearing a ring and all in all would be a better ending.
My only annoyance is that the kids are wearing the exact same clothes as in his dreams. Either this was sloppy on the directors part, or its a dream...
Also there is one very large plot hole. A "kick" brings you up from the level below. A kick wont work if you are not in the level below, but rather 2 levels below, as you would need two kicks to be brought up to that level. This explains that when the van goes off the bridge the team isnt kicked to level one, as they are still in level three since arthur could not set up the kick in time. The plot hole is, ARTHUR IS IN LEVEL TWO!! He shouldve been kicked up to level one alone... But I dont expect every plot hole to be accounted for in a movie like this. The plot holes in every other science fiction film are ten fold this one... Just food for thought