A.V. Club: "Left 4 Dead, the new co-operative shooter from the makers of Half-Life and Portal, comes down on the fast side of the zombie speed debate. And it's about time sprinting ghouls had their shot in videogames. George Romero traditionalists may balk, but running ghouls work well in the context of consoles. Shooters depend on forward momentum: Allow players to linger too long, and they obsessively scour every nook for bullets and health boosters. In Left 4 Dead, there's no such thing as a clean room: Hang around, and the game's "director" will throw more zombies at you. And when dozens of undead tweakers come booking at you from the darkness, it's hard not pull a Cosby-first you say the expletive, then you fill your shorts with the stuff."