Picked up Prey a few weeks back when it was on sale. From reviews people seemed to like it or hate it. Most complaints were that it was a short game, lacked difficulty and not very innovative with its portals or gravity walking. Maybe since I picked it up cheap I was more lenient but I enjoyed it for a run and gun game with a few twists (Nice change of pace from the tac-sims I usually play). Probably helps that I dig sci-fi too. It took me about 9hrs to play which is comparible to most new games now so I don't see why its considered more short (Guess some rushed to beat it in 6hrs but I like to check out all the corners of the maps)
Prey's levels of a spaceship sometimes reminded me of Riddick though Prey adds a bunch of weird organic parts to the levels. Sometimes felt like I was running through a cyborg's colon or something. The gravity walking/flipping was a fun and different way to do in-game puzzles. Portals didn't do much except act as doors but they still looked pretty and were a logical source of enemies spawning as opposed to monster closets.
The story was decent and I liked the levels/atmosphere of the ship. Enemies were mostly brute AIs to be cleared. The soldier version seemed to get smarter toward the end of the game but for most of it they were clumsy fodder to get past. I knew this coming into the game and was mostly playing to enjoy the story and levels. I wasn't looking for the greatest AI ever as most games lack in that department anyways. The weapons were weird looking but most acted like most fps guns once you figured out what they were.
I thought the difficulty was fine and didn't mind the spirit death part. Helped the game flow smoothly since there wasn't a break in playing the game. Those that don't like it could just reload to skip it if they though it cheapened their victory in someway (I'm playing to enjoy the game not as some competition). Also liked the use of the spirit to find secrets and get past puzzles in the game.
Enjoyed it overall and still not sure why it was bashed by some. It wasn't the greatest title ever but it was good. Maybe it helps that I haven't played Quake 4 yet though my playing of Riddick didn't make me not enjoy Prey. I'm not sure what other games came out at the time so not sure what its new game competition was. It also helps that I got it cheap. I also don't bash it for not being super innovative as I don't feel most new games go much beyond what I've already played (Just slap a bit of prettier graphics/physics but not actual gameplay).
I did find a few mods but didn't really try them yet:
Filefront has a few mods that are mostly either weapon tweaks or AI mods. I briefly tried the AI mod after finishing the game and it did seem to toughen up the AI and the earlier soldiers moved a bit more. I didn't play with it enough to get a good gauge it the changes but it does seem like an option for those who feel the game is too easy.
Also found a level mod called Altered Reality on ModDB. Seems to be one of the few SP levels. I might try it one day but have other games I want to get to first.