Circular Ending (Spoiler)...
I've noticed a lot of people assume that the events of the film will play out again in reality after the movie finishes; surely it would have to happen differently this time, because Dean would have the memory of his extraordinarily vivid dream to guide him? He would know how to kill the infected, he would know to get home and collect his wife straight away instead of going back to work etc.
I've given this far too much thought, obviously...