I've been a fan of director/writer Christopher Nolan ever since "Memento."
This film comes with much hype and I dare to say... having just seen this... much of it is over-hype in my opinion.
Beautiful to look at (it seems that a good majority of the $160 million budget went into special effects) and somewhat interesting to think about afterwards (three levels of dream world, well, actually four...), at the end of the day the story didn't have an effective emotional core to really hold an interest.
Part of the problem lies in the dream landscape itself. If the audience knows that what they're watching is a "dream" then they effectively know that it's not real and subsequently can't invest themselves in the story.
There are quite a number of references to other films (Citizen Kane, James Bond, Matrix, Blade Runner...) and a global cast (think international box office).
I'm not sure that Leonardo Di Caprio was the best fit for the lead character, Cobb. He doesn't have the maturity and intelligence that Cobb would need to have to truly pull this story off. Cobb would need to be at least 10-15 years older...
I must say that it's nice to see a summer Hollywood film that's creative and fairly unique rather than another sequel or remake...