I actually am lost by the ending of this movie but I do have some interesting points to make that support the ending being a dream or reality. Also here is an answer for th person asking about totems "YOU know your totem's trick exactly so if you were in your own host dream then you could replicate it perfectly. It is only when you are in someone else's dream that your totem does not behave in it's trick form since that host cannot architect it so. This is why nobody knows the trick functionality of anyone else's totem!"
If it was a dream it would make sense because we are never certain that the entire movie wasn't a dream due to his wife holding the totem, children never aged even though he got a call from them earlier in the movie with them sounding older, they were wearing the same clothes as before and at the same place in his dream.
The only argument I have for the ending was the Cob's totem behaving in the only way it would in reality because if you did listen closely at the ending it wobbles proving the totem rule stated earlier. Theres also a quote from Dileep Rao (Yusuf) "Close your eyes and listen to the sound at the end. I really do think the top wobbles and that it's real." It also helps to answer a lot of questions check it out here's the link
http://nymag.com/daily/entertainment/2010/07/inceptions_dileep_rao_answers.html