I feel sort of cheated, to be honest (although I'll reserve my final judgment until I've seen the movie). From what all the people who've seen the movie are saying, it's nowhere near as original/different/groundbreaking/thought provoking as Ridley, Damon, and the rest of the cast have claimed it to be.
I personally attribute that to the fact that "different" usually doesn't bode well with the general audience, and at the end of the day, Ridley and co. want the movie to sell well. If he had delved a deeper into this new mythos surrounding the Engineers, their past, their intentions, etc., and made Prometheus a standalone film (with an ambiguous ending, for a potential sequel's sake), I believe that it would have been much better. It seems like they dumbed it down to cater to the "general audience."
Of course, I haven't seen the movie yet, so I might end up eating my own words once I have.