Its because it's a port basically.
I bet yah they didn't slow down a lot and the console guys just can't keep up. I found anyways the turning and such to be slower on the console then how I had it on PC when I was playing L4D1.
The other thing too people were just stomping on them about the first game not being long enough and fairly easy (ie me), now they changed it and people don't like how everything is longer and harder. Such is the life at Valve.
I still refuse to buy it btw