Once upon a time, Alan Wake was a game coming for both the PC and Xbox 360. Then mention of the PC version began to simply disappear, culminating in the final announcement yesterday that the game's for the 360 only.
A statement from Microsoft reads:
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.
So there you have it. Pity, but given the absence of material or promotion for a PC version, hardly surprising.
Microsoft: Alan Wake will no longer be coming to the PC [Strategy Informer]