Sorry for the slowness, had to sort out family stuff.
Played it for a while and it's been great. Better performance than I was expecting really. I think RAM must be the biggest requirement for ARMA given how well it runs on my iMac compared to my gaming rig which is otherwise much beefier but only has 8GB RAM. 12GB feels like it makes a big difference.
I'll install fraps and things and upload some footage.. At native 1920x1080 res its smooth at medium settings... If you're happy downing the 3D resolution you can run it at high to very high on everything except draw distance. Until fraps is working i dont know exactly how fast so bear with me.