Now, reader, keep in mind that you may not want to read this as they do include super plot spoilers. This is only for people that have seen the movie and I don't want to ruin anything for those who haven't seen it.
So Escapist, what do you think?
Okay. So, in the end of the movie, Cobb goes stays in his level of the dream world while Ariadne leaves. This is because Cobb believes he can still save Saito from dying thus allowing him to go back to his children. For a while all goes well. Saito is found in the dreams, as an old man, and everyone wakes up as normal. Saito makes the call and Cobb is able to go back to his children. However, when back at his house, he takes his "totem", the spinning top, and spins it. Just as it appears to start to topple, the screen cuts to black.
This discussion is basically about whether Cobb lived in a fantasy world or reality at the end of the movie. Since Nolan gives us no answers (and I don't think he's supposed to} we draw that conclusion himself. As for me, I think that question is entirely irrelevant (I know... it's my question). The entire point for this job was to get back to his kids and that's what he has done, if he lived or died. I don't think he ever left the dream but has instead created an alternative reality in his head.
So Escapist, what do you think?