^ Actually the more I think about the reasons put forth by everybody, the more I think it *must* be reality. And then I get more confused as to why Nolan would choose to end on the reality/dream question-mark. It makes it nothing more than an affectation rather than any genuine conundrum.
And therefore I go back to the there-must-be-more-reasons-for-it-to-be-a-dream way of thinking... But what? Except that he deliberately sets that up.
I think he puts the doubt in there just for the question mark, just to start discussion. Look at this very forum, three, four threads on this movie and in them discussion on whether or not people thought the ending was in "reality" or still in the "dream"? We couldn't have this disucssion if the ending was obvious and clear-cut. That's great film-making, something as simple as the white-flash at the end of "Total Recall" is the movie the "real world" or was it the memory implant Quaid had paid for?
Watch Inception and how you want to view the ending is all going to be on how you read the movie as a whole, your own idea of what is real and not real and, I suppose, also your idea on whether or not "happy endings" are genuine.
One of my co-workers loves
unhappy endings. He's not seen this yet but he'd likely advocate for the ending being Cobb stuck in Limbo/Dreamland and he'd likely precieve the totem as being in perpetual spin. Nolan cut-off the ending just in time to give doubt. Some see the wobble, some don't. Some see the wobble as being just part of the top's spin some see it as a sign the top is about to fail.
Some see the age, and clothing, difference in the children between the ending and the visions, some don't. (The children are close-enough in age that they look "alike" but after three viewings the children are pretty differently clothed not to mention noticably
older, especially in the girl. In the memories the daughter looks to be about the age of pre-schooler or kindergartner at the end she's noticably taller and older by a couple of years and in different clothes.)
Some think that him seeing his children is really his "totem" and what's going to happen to the top doesn't matter he knows
he's in the real world. Some see that him being in a dream would make the entire movie pointless, mean that Mal had "won" and that Cobb is in his own nightmare in a dream he himself said wouldn't be good enough for him. He wanted reality.
But, some see the ending as being Cobb in the dream.
That's what good film-making is, ending the movie in such a manner to raise question and doubt no matter what the ending "really is" or what Nolan intended.