Take a look at the middle east forum on pprune. Lots of info there. Keep in mind some guys posting there are professional whiners.. but 80-90% of the stuff is accurate and true.
As for a list of things that weren't as promised.. well it would be a lot shorter to list what went right than wrong... Needless to say, do as much research as you can. Visit Dubai with the wife and have a good look around, ask lots of questions. I'm on my way out of there so I don't have a very good opinion of the place, but each to there own, just go in with your eyes wide open and get your own answers.