I want to start off by saying that if you've set your expectations (like I did) on seeing Aliens or at least some Alien "goodness", you will be very disappointed.

Rating: 7/10 (19 January 2013)

However, watching it a second time, I tried to be more objective; to see it as a separate title, not as a "Alien' prequel.
Without going very deep (because I would ruin the whole experience) I find this movie -- interesting. It's far from great, it's far from what older Sci-Fi movies have done, not to mention it's way below the bar which the Alien series has set long ago.
The plot has some problems and, the characters are rather undeveloped and some of them feel out of place (they're not relevant, given the nature of their task) and the story has a very slow pace. On the other hand, the visuals are amazing and the cinematography - spectacular, all the while the 3D implementation is somewhat pointless.
I gave it a 7 because I respect Ridley's effort and although I've been disappointed with it overall, I admit it has strong aspects. Let's face it, the movie industry is on a downward slope for some years now, and it doesn't seem to get any better when even the most respected directors disappoint.