I played it for about 4 hours with a friend tonight... I only stopped because he went to bed, and I figure I should do the same (yet here I am). It takes some getting used to, but once you're into the game, it's quite a bit of fun. Slow paced compared to what I'm used to, but I just think of it as a Fallout game, even though it's a bit faster (and so far cooler imo). I like killin zombies, and I like that my character doesn't have a ton of health. Sometimes it's just better to run and live than fight, and conserving your weapons can be important as well.
My friend rushes in and dies constantly though =\ You can't do that if you want to live... which is good.