Well, I am just playing it. I very much liked the beginning, since there is a "promise" of great things to come. The setup is interesting enough, some scenes are properly spooky, the atmosphere and the mystery seems to build up nicely.
However, there are major downsides - the actual gameplay, while built around a very nice effect of "dark forest coming all alive" (we all know it from childhood, when fantasy and fears play tricks with eyesight in the dark, only hundred times magnified), but it gets very old very quickly. There is no exploration, it's a canyon with only one way to go. The combat is based on a single trick you repeat over, over, over and over again. Later in the game, it literary turns into pain you have to endure to make it to the next non-interactive cut-scene that pushes the story forward. Early in the game, there is enough variety in environments to compensate, the daytime sequences let you rest, but now I am in the middle of the third episode and I can't force myself to play on.
Speaking of the story, there comes a moment you realize it's just a pile of cliche stirred up in a pot. It borrows heavily from Silent Hill ("am I crazy, am I making this up, do I fight monsters, or am I killing people?") and from Stephen King ("Am I a crappy writer or not? Ha I can't be, since the HELL itself is forcing me to write on"), but the characters end up being cardboard props, complete with the mandatory comical sidekick who can't act so he must talk all the time - you can find them in every American movie for some reason. There is just not enough depth in them, there are no lingering mysteries, the game does not compel you to write plot analyses longer than the script itself like Silent Hill did. In the end, it's to Silent Hill what Dan Brown is to Umberto Eco - a simplified, more accessible version of the same more suited for general public, with a convenient answer for every question the plot presents. Where Silent Hill uses symbolism, Alan Wake is content with obvious references to famous horror flicks like Shining and Birds.
IMO it's a game designed to create an early WOW wave to boost sales, but not enough effort and resources are spent to create content for mid-late stage.
However, there are good points - beautiful landscape and moody atmosphere, the dark forest trick (before it gets old), dodge move in combat (I like it very much, it's a proper horror last moment escape), and the way the game trains you to associate light with safety and darkness with threat - the setting sun in the beginning of the game is really subtly used to create an atmosphere of an unknown threat getting closer and closer... and thats it.
Technical note - PC port has problems, all the cutscenes have sound out of sync, it's maddening. Also, trees at some scenes flicker, it's super ugly. The mouse controls are crappy as with most ports, I recommend XBOX gamepad.