Prey is an artistic, creative game that could have been better, but still delivers a fun experience.
Pros: Great graphics, story isn't amazingly unusual, but the setting is creepy, and very well done, with attention to details...a nice imagining of an alien abduction, nice handling of environment, good dialogue, interesting main character, fantastic music....loved the soundtrack, fairly interesting weapons, fairly interesting creatures, wall walking was fun and portals were fun, a few interesting portal related puzzles.
Cons: Not enough action, not enough variey of enemies although the ones present are interesting, needs better pacing, too much isolation, some isolation is good for creepiness, but here it's a little too much, wall walking was cool, but more puzzles are needed, portals were not used to full effect.
In short, this game is easily worth buying for $30, or used for even less. Even though it has flaws it was an enjoyable experience and if you like FPS's or thought out alien environments you may enjoy this game.
I WOULD buy PREY 2 should they make it assuming the game is even better than the first.