It took just under 2 years, but it is finally here on the PC. You can buy the game through steam for £22.99 for the UK and $29.99 for the US.
Just thought I'd tell you too that for a limited time, you'll get the collectors edition for those prices instead of the standard edition. This includes the Soundtrack, The Alan Wake Files in PDF and the Developers commentary. This is up until the 23rd February 2012 so you better hurry!
Alan Wake PC: http://store.steampowered.com/app/108710/