Alan Wake was originally announced for PC and "next generation consoles" back in 2005. In July 2009, Remedy revealed that the fate of the PC edition was "up in the air," later clarifying that it "would love to see a PC version available to its PC followers" but stressing that "this decision lies with our publisher."
As publisher Microsoft explained to Strategy Informer:
Some games are more suited for the intimacy of the PC, and others are best played from the couch in front of a larger TV screen. We ultimately realised that the most compelling way to experience "Alan Wake" was on the Xbox 360 platform, so we focused on making it an Xbox 360 exclusive. Both Microsoft and Remedy have long histories in PC game development. This decision was about matching this specific game to the right platform.
The game represents the first major release out of Remedy Entertainment in close to seven years, its last being Max Payne 2: The Fall of Max Payne in October 2003.
This is very unfortunate news
Yeah, definitely agreed. I was probably going to purchase this on release for PC. Now I'll probably wait until I get a used copy on 360. =/ Obviously that won't be the norm, but it is certainly disappointing.