Time for me to pipe in now....
First of all, this movie is brilliant, clearly. I've not been this impressed by a sci-fi movie in the theatres since Minority Report.
As for the current discussion about the nature of dreams, this movie's quality does not rise or fall based on how accurately it depicts the nature of dreaming. Perhaps some people dream in surrealistic Dali imagery, and maybe others dream in realism - who cares? That's not even remotely relevant to our enjoyment of this film. Science fiction has a long and, sometimes, illustrious history of creating plots in which people cannot judge whether what they experience is reality or a fantasy. This film is inspired primarily by Philip K. Dick, whose Three Stigmata of Palmer Eldritch it most closely resembles. And in that book, as in this movie, the dream setting is merely a metaphor anyway for our own experiences of living life - how can we be sure that how we perceive the world is how others perceive it? How can we trust our own memories of events, if those memories are edited by our own subconscious so as to make sense of them? When I think of an ex-wife, am I remembering her as she was, or remembering only my memory or perception of her? (Solaris dealt with a similar issue.)
The idea here is not to capture precisely what it feels like to dream. The idea here is to explore the psychology of memory and fantasy and perception and identity. The dream plot is a metaphor, like most of the best science fiction plots.