It was meant to be the killer game to sell Vista systems, as it was to be Vista exclusive. Unfortunately Microsoft wanted it as an X360 exclusive; they paid off the developer and the PC version was jettisoned. Pretty sad that in an era when more and more publishers / developers are supporting the PC in multiplatform releases that Microsoft - the developer of the Windows platform - is going in the opposite direction, destroying the Halo 2 port and buying up content (why couldn't the GTA4 DLC be released for PC?).
Still, it's not really a big loss. In catering to the console audience they shifted the focus of the game from survival horror / thriller to action horror, which is of much less interest to me. The recent video I saw of it looked pretty weak.