It's an intriguing idea.
An elite gang of psychic agents, infiltrating the dreams of others by creating elaborate subconscious scenarios to steal information and possibly plant new ideas in the minds of their victims. The visual effects are fantastic, with Escher like staircases, cities folding in on themselves and strange shifts in gravity, and the soundtrack gives the DTS surround sound a good workout too.
Unfortunately, that's as far as the good stuff goes. The film is an overlong (two and a half hours!) muddle, that has exposition where it should just show and changes the rules as it goes along (if you die in a dream, you wake up, except in some dreams where you get stuck in limbo. Or something).
The major problem is that the dream sequences are not imaginative or dream like enough. Instead of the furthest reaches of imagination, we get some not very original car chases and shoot outs. Instead of altering somebody's psyche for some vital reason, it's to get a business man to sell some shares in his father's company which is up there with the trade disputes of Star Wars episode One for dull plot points. At no point in the film does anybody dream about going to school and realising they are not wearing any pants. I rest my case.
Ironically enough, I nodded off fifteen minutes from the end for a couple of minutes, but I don't think I missed anything.