inception (spoilers)

[mstevens]

The top isn't Cobb's totem - it was his wife's. Remember that to work a totem should never be used by anyone else. Cobb's actual totem, in my opinion, is his wedding ring. He wears it in dreams but not in "reality." That would make it the only totem that isn't a game piece.

Cobb is interrupted running to the bathroom to check the top. From then on we have no way of telling what is dream and what is not.

A totem tells you only if you are in someone else's dream. It doesn't help you figure out if you are in your own dream.

The kids' clothing does change - they wear black shoes in all their scenes except the end, when they wear white shoes. They are portrayed by 2 sets of actors of different ages and the credits give the ages of the same characters 2 years apart, so their age and appearance also change.

We are the ones who want to know if the top falls. Cobb leaves the top because he no longer cares if it falls or not. As the movie's slogan says, "The dream is real." That's all that matters to him.