Interesting, I am glad to hear it isn't just me.
I was running a fairly mimimum pc with no lag, but with only 2 gb RAM I was hitting near the max my comp could handle, so I ran out yesterday and bought a new pc..
8 GB RAM, AMD A8-3800 Quad Core Processor, ATi Radeon HD 4670 vid card...now my FPS is terrible and I lag so much I have a hard time moving in the game.
My new PC may not be top of the line, but it shouldn't be running MUCH MUCH WORSE than my old system....
Not to mention the game seems to lag my entire PC.