I also just picked this up. I got it in the Christmas sale for £6, defo worth it. Just like Audiophile I don't really like zombie games, but it was Fallout 3 that got me a little more used to the situation. And my love for looting in a post apocalyptic wastland is stronger now than my dislike for zombies.
I only have the end mission to do and I have mopped up all achievements pretty easily none were hard at all. All I have left is to blow up a character in a blaze of glory. But like everyone else I keep a copy of my savegame on an external drive. (I extremely dislike games that don't let you have a manual save) Fallout 3 was the best, save where ever and whenever you want. Permadeath wouldn't be that big of a deal if you could just have manual saves.
Anyway, the game is great, though originally I disliked the sluggish movement, awful animations and insane lag and bugs. But overall it is much better once you get out into the rest of the game world.
My only issue with the game is the inventory system, it uses weight, but it uses a max amount of slots as well which makes no sense. I wish I could just pick a character to start with, and just get looting in a free roam world and pick everything I care about and keep on me just like you can in fallout. I want all the ammo I find on me, same goes for meds. The reason this is important is that the storage in this game sucks, you put a sh*tload in and either the AI takes it or it gets removed and at one point you might have over 100 rounds of each ammo type in the locker, then all of a sudden they all f*ck off. I want a personal safe that does not get edited at the very least.
I don't know much about the DLC other than its some sort of non story free roam, is it really worth paying what I paid for the whole game just to play a different game mode?