I played the demo of Prey, got to say I was extremely satisfied with it. From the start where the characters spoke and their mouths were lip synced to the voices so well it looked like a real person was talking almost.
The graphics on this game are superb, perhaps one of the best optimized game engines i've ever seen. The way the aliens abducted you was fairly impressive.
Next thing that I thought was REALLY cool was the portals, I was amazed by that, so simple but it works. You look through and you see another room, walk around it and you see the wall to the room you're in, that is so freaky in a way and yet so cool.
Next awesome thing I encountered was the gravity walls, blueish looking thing that I could actually walk up, that was great. It was only a demo but I seriously want the full game now... could be a candidate for game of the year.
I score the demo 10/10, perfect.