I just saw it this afternoon and thought it was very good. Upon relfection it seems complex but as I was watching the movie I wasn't concerned with how complex it was; the film was so fast-paced I didn't have to think I could just enjoy.
I agree that some of the characters weren't fleshed out to a great degree, but the cast was great and brought some personality and likeability to their characters.
I thought sometimes the slo-mo was a bit unnecessary (like when the van was turning a corner).
Also the vault where Fisher saw his father in the Alpine Hospital reminded me a lot of a Holodeck.
And the last shot did annoy me a bit, seemed like it was just in there to get people questioning. Which is fair enough Mr. Nolan has the right to do that.
Oh and I think it was the real world at the end.