Well, fair play to Bohemia for releasing a demo. I'll certainly give it a go, as I was really looking forward to it.
I would imagine that as it is a slow, tactical game, 30fps may just cut it.
With a Quad Q6600 at 3.4Ghz and a GTX 260 OC on XP, I'm hoping it will look reasonable at 30 fps, on a 1680x1050 monitor.
After all, I'm on High settings in Crysis with a minimum of 40fps....although i know there's not that much going on compared to Arma2.
BTW, does it support any AA ? I really hate jaggies.