Before I start, my PC specs:
Intel Core i7 920 @ 3.5GHz.
Dual ATI HD5870 1GB.
Corsair Force GT 240GB SSD.
For some strange reason I get REALLY stuttery gameplay, the worst I've experienced so far was when all the zombies were coming out of the wood, it kept freezing for 2-3 seconds and I could only hear what was going on (I couldn't see it happening) for 2-3 seconds after each camera angle change.
I have the latest graphics drivers so I'm not sure why this is happening.