The major fault with the PC version is that it has DRM (SecuROM) on it. I was very excited to get the game when it came out on the Xbox 360, but reviews came out saying that the game had technical problems (long load times, pop-in, etc.,) and a terrible inventory system so I waited for the inevitable PC version. The PC version finally came out...but had SecuROM on it, so I refused to buy it. I finally rented the Xbox 360 version and had a really good time with it. I installed it to my hard drive, and while the elevators can be slow, and there is pop-in, it doesn't break the game.
Short version? I recommend that you wait for the two-disk version to come out in a few weeks and get it for the Xbox 360. If only because I have an undying hatred for DRM.