I've played and finished Alan Wake on Xbox 360 a long time ago, and the PC version of the game has been recently released. Is there any difference between the two?
The only differences between the two will be difference in graphic.
Quote from official Alan Wake forum :
There are a few differences - the engine is basically the same, as is the gameplay, but we've increased the engine quality settings on many areas including draw distance, shadow quality, post processing etc. We've of course included the Signal and The Writer with the game too.
You can see PC vs Xbox 360 screenshot comparison here.
And you can read even more about the graphical differences here.