'Dream a little bigger darling' says Tom Hardy at one point in the movie. I wish the film had taken his advice. Perhaps because of it's origins as a lower budgeted script Inception never really takes advantage of the idea that dreams can be pretty much anything. The characters' idea of dreamer bigger is to have a larger weapon. But it's still a weapon. Rules are set up to excuse why things don't get too wacky, but the movie made up the rules which don't really make sense anyway.
Apart from that (and a few of the usual Nolan tics - dead wives, chilly characters, very few good jokes) it is a pretty good mix of Phillip k. Dick and James Bond. A large (too long - another Nolan problem) section late in the film serves as a love letter to On Her Majesty's Secret Service and I suppose it's no accident we see Dicaprio first suited up in a tux.
The action is solid if unremarkable, better than many of his other films and it manages a consistant throughline of where (reality wise) everything is that is going on.
Also bolstered by an interesting and capable cast.