This is definitely a thinking person's sci fi thriller, but the constant and unstoppable gun battles and violence overcome the subtleties of the premise. There is just too much going on here at any one time.
I have no problem with suspending reality, but there needs to be some internal consistency of logic or other basis for believing the premise. Either I missed it, or there was never an effort to explain how the characters can go in and out of others' dreams as they do.
Special effects and acting are great, and ii does make one think afterward which is a good test of a good movie.