There's a brief scene where we see Cobb breaking into Mal's safe and inspecting her totem, the top. Presumably that's part of how he planted ideas in her head - he knew her totem. But since the top is Mal's totem, what's Cobb's? His wedding ring! Which we see in all of his dream sequences, but none of the reality sequences. So whether the top stops spinning or not in the final scene is irrelevant. What counts is, is Cobb wearing his wedding ring or not?
Edit 2010/12/13: I haven't seen an original or/and interesting comment to this entry in two months plus. Just endless anonymous drive-by "yes it is!" "no it isn't!" repetition. Super-boring and mega-pointless. So commenting on this post is now disabled. If you really believe you have something original to add that hasn't already been covered by a pre-existing comment below, why don't you give me a call? My cell phone number is in my LJ userinfo. If you won't even take the time to explain it to me on the phone, they I doubt it's good enough to make a new comment over...