There's something to be said for getting rushed with Zombies and fending off those a-holes when they're takin down your friends, but I hope Valve gets creative with the types of Zombies. Wall crawlers, grunts, tanks, speedy, invisible..... you can only do so many. I just hope it doesn't feel repetitive.
The premise sounds very fun. I like how Gabe commented that he plays as the female character, because guys feel that they need to protect the girl, and he lets sexism work for him. Classic!