I enjoyed Prometheus for the most part. I thought the last half hour or so felt rushed somehow, badly edited perhaps. It didn't spoil the whole film or anything but it did leave a bit of a bad taste. I guess I'd give the movie 3 out of 5.
The only character I liked and found interesting was David. I can't stand Noomi Rapace and found it a chore watching her (if you need to flame me for my dislike of Noomi then flame away). I didn't think much of the dialogue and with the exception of the Engineer I didn't like the creature designs.
I did like the general look of the film, liked the sets and non-creature designs, like the effects etc. Even the story isn't new in terms of alien astronaught stuff I did enjoy it apart from the last 30 mins.
I didn't have a problem that with not being a direct prequel to alien and not seeing the classic xeno, in fact I think it should have been totally divorced from the alien movies, set it in a completely different universe.
This is one of those movies I'll probably only watch once. Not neccesarily a bad thing, I've only seen lots of good movies only once, however this is the only alien related movie that I'll have only watch the once.