One thing that's been constant in all previews of L4D has been the attempt to instill a fear of the Witch in all readers. Naturally, this means that everyone wants to shoot the Witch because they've been told not to. Fortunately, while startling her is undoubtedly detrimental to your health, the fact that she stands triumphantly over you after knocking you over means that everyone else can then kill her without too much trouble.
But note: THAT DOESN'T MEAN YOU SHOULD SHOOT HER.
Nor should you fire at abandoned cars in the street to alert the horde, and bring innumerable droves of the undead sprinting from every direction just because you want to kill more zombies.
It happens all the time though, doesn't it? It's sod's law. You tell someone not to do something, so they do, because they're a twat. Perhaps if all the previews had said "Setting car alarms off starts happy-happy-fun-time!", no-one would do it.
Still, despite the vast majority of L4D players being twats, it is an incredibly fun game. Although the demo is only one and a half levels long, it's too easy to waste hours on it. Valve have obvious spent the most attention on co-op, and consequently the single player is shite (Read: Decent enough because it's a Valve game anyway and they never fail OMG I love Valve plz secks meh).
I have a couple of issues with it. I think it would be better to stay in first person when you're pinned by a hunter, as I do so enjoy soiling myself. Also, there's... umm...
Alright, there's nothing else wrong, it's absolutely brilliant. Playing with the Three Alexateers last night was the best fun I've had in ages. Valve dominate single player with HL2, multiplayer with TF2, and now co-op with L4D. And they do make for some lovely abbreviations. Friendly fire is permanently on, but meleeing teammates doesn't hurt, so it's fun to watch their heads bobble about as you hammer the right mouse button. I love the the horror movie style "Save yourself!" moments, followed by hiding in a cupboard with a grumpy Ralf Harris lookalike. I love the selfish teamplay, when the player lowest on health is the one chosen to molotov the Witch in the face.
I love the toilet:
But I do hate it when gay sailors shut the door, ending the mission. Why did you do that?