I can take or leave Leonardo Di Caprio, but the real character and star of the movie is the team he puts together as a whole. These are the companions you want to have in classic Traveller. Here they are travelling the subconscious but by Crom you'd want them at your side as you took on the universe, any universe.
The film builds up with the first half trying to convince you that the premise of the movie is possible. The second half is rip-roaring action and does have a genuine dreamlike quality of the real and surreal happening side by side. It builds up into an assault on a snow fortress which has all the feel and energy of a Call of Duty: Black Ops mission.
Must admit that I would have preferred Jennifer Connolly in the lead female role. She was excellent opposite Di Caprio in Blood Diamond. That aside - don't sweat the possibilities or reality behind the movie and even just for the last half which is Matrix meets Call of Duty: Black Ops - worth watching.