Not as scary as Alien and not as thrilling as Aliens this is a different type of monster film altogether and a pretty good one. The script gets a little murky at times and there are too many characters but this is one beautifully put-together film. It's gorgeous to look at (pretty much a given with a Ridley Scott movie) and there are some excellent performances. Not surprisingly I was riveted by Michael Fassbender's artificial life-form David but I really enjoyed Idris Elba's laid-back Captain of the ship.
The "operation" that takes place about halfway through the film is a classic gross-out scene and one of the best bits in the film.