One of the best zombie games I have played so far. The World War 2 setting really adds to the atmosphere and it is a nice break from the horde-style "shoot em ups" like Wolfenstein. Single player is extremely difficult, the game is obviously made for multiplayer. The only changes I would like to see would be able to create barricades in doorways, like Killing Floor, maybe some character options or talents.
Call of Duty wishes they could make a zombie mode as fantastic as this. I just wish the multiplayer community was more active, took me a little while to get a match-maker system, can see this being a ball when playing on Skype with mates on this one.