Just came back from it. It was solid, I really really enjoyed it BUT - there was nothing here that made my chest thump and brain race. This film did not get me excited, which is a little bit of a shame. The trailers did give away a LOT of the big points which sucked. There is still some stuff there to make you go "ooo", but overall I'd say about 50% of the big stuff is ruined plain as day in the trailer, and having seen the film another 20% is there even if you don't realize what it is.
Don't get me wrong. It IS a great film, and is worthy of being connected to the Alien franchise in a prequel-ish way (c'mon it IS. Sort of. It's more of a prequel than its not). The way it leads to a possible sequel is not what I would called hackneyed or tacked on, it works. It certainly adds too Alien as a film, and does not detract in any way.