Haven't played in a while... It's quiet a bit different now. Everyone just shoots on sight. Got into to fire fights just spawning... murdered two people already. :/
I recall someone mentioning a nvidia specific tweak to get some more performance out of this game. Tweaking the max pre-rendered frames? Anyone remember?
It was Max Pre-rendered Frames to 8 or as high as you can get, but I'm not sure if it's much help these days. That can also be set by configuring some Arma2 files, but I don't know much about it.
My tip on how to get the best FPS: Play on a freshly restarted server. You can sort all servers by status and look for "Setting Up" "Briefing" or "Waiting". Those servers have just restarted and have by far the best FPS you'll ever see. If your FPS sucks there, then it's your PC. This tip most likely will be obsolete in a couple of days with 1.7.1