Okay, so it's a bit of an older title but:
I am about 2/3 of the way through and this is SO FUN!!
I haven't had as much fun in a game since.....well, the first Half-Life.
My fav chapter so far is "Highway 17" for the crane and bridge sequences. What a giggle.
Well worth the money and I wish I picked it up earlier.
I just hate the head-crab zombies though....well, i hate any zombies and creepy stuff.
