I think I have to agree with Scotts- all I've seen at this point is the trailer and the posts in this thread, but it seems to me that this is a story told in the Alien verse with no connections to the Alien stories. The Alien stories tell about humans contact and interactions with the xenos, while Prometheus tells about humans contact with something else- apparently the space jockey race or whatever they are. The fact that the space jockey and Weyland Yutani are in this film just means that they are part of the same universe.
I see it as something like archaeologists finding a lost pyramid in Mexico that's been hit by looters. The xenos are the looters, and the Alien films follow Ridley's adventures with them, while Prometheus goes back to tell the story of whoever made the pyramid in the first place.
That's the impression I get at this point, but regardless, Ridley Scott and the Alien verse has me squeeing like a little girl at a puppy party.