Ten years is a pretty long time to make a game, but I think it was worth it.
Prey's storyline is fairly uniform, with a few discerning elements. Tommy, the game's protagonist, is a former US Army mechanic. He's also of Cherokee descent, so he lives on the Cherokee reservation in the Midwest USA. But, of course, he hates it there. He wants to move away, but his girlfriend doesn't want to move. He thinks of his grandfather as just another spiritual nut, the kind that banters about old religious mythos as if it were really true.
Of course, Tommy tries to convince his girlfriend to at least come with him for a few days. A couple minutes and a bar fight with drunken rednecks later, the roof disappears and an alien ship hauls everyone into itself.
From there, Tommy's only goal is to escape with his family. The game's plot takes some interesting turns, and it makes for some good thinking, but it's none too complex.
Tommy starts off the same way every distraught hero-to-be starts off- with basically nothing. He's got eight weapons to fight with, though you rarely use the wrench after you grab your first weapon. From there, it's typical FPS fare.
The difference with Prey, though, is that it uses several distinct twists to the gameplay to make it more interesting. Portals are the first thing they tout, but the problem, like Gerstmann asserted, is that they aren't used to maximum effect. The problem is linear level design. It's an awesome special effect when they present it like a door instead of a glowing ring of space, but it's still basically a doorway. In order to use it to better effect, it would be better to make a more non-linear environment.
Gravity walls are pretty cool since they change up the combat a bit. I think this feature reaches better potential than the portals. Plus, it's neat to see a room from impossible angles.
Spirit walking is interesting, and it lets you accomplish some interesting puzzles. You have a weapon in this mode, and it's great for sneaking up on enemies. Still, you won't be using it as much as your typical arsenal of weapons. I think they could have made some more complex puzzles with this and other elements combined together, but they didn't. 'Course, 3D Realms' last game was Duke Nukem. What do you expect? Maybe they'll do it some other time if they get smart enough.
Gravity changing produced unique puzzles, and I think it was implemented well. All in all, their most vaunted features were the least used.
But with gravity manipulation and the exoskeleton suit, Human Head was allowed to make some crazy ideas work. And they pay off- but the coolest stuff are the huge environmnents, like the asteroids that you can walk on in the middle of a giant chasm. That's always cool. The scenic route is very rewarding in that respect. But you'll be crawling around on the inside of the ship a lot more than exploring the epic size of the Sphere. So, recapping, the gameplay is pretty standard, but the unique elements are pretty good, save for the portals. They need to do something about that in the next Prey game. (They explicitly say at the end that 'Prey will continue', but I'm not spoiling anything by saying that since that's an announcement that probably woulda happened sometime in the future anyway. If it sells well, anyhow.)
On one hand, the story seems short. You find attachment to the characters, but it's not much. On the other hand, if it were longer it would drive me insane since most of the time you're just trudging through corridors. So it's a win-lose situation. Either way, one thing suffers for the sake of something else.
The music is great. I really like the effort they put into the soundtrack with the epic scores and dramatic music. Hearing "Don't Fear the Reaper" while you're being abducted is pretty cool too. 'Course, you only get to hear these soundtracks in the beginning- though after you beat the game you get a 'Casino Mode', so I guess you can go back and listen to the songs to your heart's content. I haven't done it yet.
Of course, replayability is limited. There are some fun times to be had, and I personally don't get tired of the FPS combat in any good game for a long time so I could probably play this again. But it's a linear adventure so replayability is limited. Still, if there's some secret to unlock by playing Cherokee mode, then I guess there's a good reason to go back.
So, overall the game is very well done, if a little bit lacking. It's good for FPS fans, but it could have been better in some respects. 'Course, that doesn't mean the game is a bad purchase. If you're still iffy on it, wait a few months for a price drop. It'll definitely be worth it then.