performance issues in arma2/dayz are mostly caused by the configuration - which can literally take even a high end pc to single digit frames per second with a mislabeled option.
as noises noted on page 1 - make sure 3d and interface resulotuions are set to same number (mismatch between these can make a gigantic difference)
also make sure the video memory is set to (default) - another counter intuitive/mislabeled option that can eat all the system resources and give bad performance in return.
post processing/object detail/shadows etc - disabling or setting these to very low also helps a lot.
This game can run on fairly old hardware so keep at it imo.
Btw, some servers are full on dodgy - good hardware + good set up - and you get 10 fps ? bad server. try a few low pop ones to make sure it's not the server that's causing graphical lag.
That's right. servers in arma2 CAN (and quite often do) cause graphics lag/low fps. It's pretty bizarre but apparently that's part of the charm