I REALLY disagree. The game is poorly optimised, or at least the demo is.
I have a ASUS A8N-SLI Mobo
Two SLi Linked nVidia 7600 GT's
2GB's of RAM
AMD Athlon 64 X2 Dual Core processor 3800+
The game gets rediculously laggy when you're playing anything but the COOP mission. The main reason for this is that NPC's spawn when you get near to their bases, and they don't stop spawning or despawn when you get far away. If I could run a dedicated server on one processor and the client on the other, things would be fine, but so far, the dedi exe doesn't work with the demo and the -server switch doesn't either.
The demo has really been a disappointment to me. There are tons of bugs, though the game is the most realistic thing I've ever seen, some things are fucking rediculous, and the lag gets so bad when I host, after 10 minutes I can't even play.