I did enjoy the game when I first played it, the setting, narrative, etc was really good. However i felt it got rather repetitive in gameplay towards the end, i feel it needed something extra in it to make it really sing.
The dlc was just terrible imo, i hope they can come up with extra mechanics for it if they ever make another one.
As for a horror game, hmm, i must admit i never found it very scary, looking at Biglee post above i felt kinda the same about dead space, there were moments in it that caught me of guard and gave me a fright or had somehow managed to build apprehension in me. alan wake never did that to me.