fantastic cinematography, e.g. the shots out of space were simply beautiful. The actors did a good job and the movie was atmospheric - but ultimately the script just did not succeed. There were also numerous changes to the Alien mythology, which made me dislike the movie somewhat - e.g. aliens growing within its host in a matter of minutes, rather than days or weeks. I do not quite understand why this was necessary.
Also, as already with Prometheus, too many characters make extremely stupid actions.