I saw it last night, and was disappointed. The first half is good, and promising, but everything from the C-Section onwards is rushed through at breakneck speed, the pacing is all off, and people start doing some weird and inexplicable things. Why did the two guys sacrifice themselves with a big smile on their faces at the end, when they could have just hopped into the standalone unit? Nobody in their right mind would do that after the Captain just said he could handle it alone. The C-Section scene itself was absurd as well.
And why cast Guy Pearce? He's a good actor, but unless they have some plan for a sequel, why not cast an old guy to play the old guy? He was not convincing as an old man.
Good stuff? Well, the effects and production design were great, and there is some good tension and good scenes in the first hour.
The complete and sudden collapse of the film into stupidity reminded me alot of Sunshine. I am such a big fan of Alien & Blade Runner, I really expected so much more from Scott's return to Sci-Fi. I gave it a B-, it was OK by the standard of most blockbuster action/sci-fi movies, but a disaster for a Ridley Scott movie.