Inception

This is a really good satisfying film (I know way to go out on a limb there Eric), that takes an elaborate heist story and mixes with a the dream world of films like Eternal Sunshine of the Spotless Mind. Its well executed, and gripping, and I think it would have worked just as well even if the ambiguity abouts its reality that's introduced at its end wasn't included. However since this is the element that's intended to generate the most discussion let me throw in my opinion on whether or not the whole thing was a dream or not, which I warn you isn't that interesting (needless to say Spoilers ahead):

Anyway I do think at least a portion of the film is taking place in DiCaprio's dream (how much I can't say), not because of the top's continued spinning, but because his kids look exactly the same age at the end as they did in his flashbacks. I suspect that the entire opening sequence is 'real' but sometime after the introduction of Ellen Page's character is when we start to spin off into the alternate reality. That's it. I'm sure a google search will yield a plethora of more detailed theories.

My real point, and what I think is the film's real strength, is that I can't say that my enjoyment of the film is effected one way or another by the 'reality' of what happened. This is what elevates it above a lot of other 'twist' films in that it holds up just fine without the change in direction. The ambiguity definitely adds some more room for thought, but just serves to enhance the story rather than dominate it. This places it closer to The Usual Suspects than say most of the works of M. Night whatshisname.