When I load up ARMA 3 everything is very responsive and extremely quick while playing on a server until I get into a vehicle and travel in it for a bit. Soon as I exit the graphics are very slow and sluggish. Dying in game doesn't fix it, reconnecting to a server doesn't fix it, I actually have to quit the game to get my awesome performance back. If I stay out of Vehicles the game runs great.
This is using Dual SLI with K5000 Quadro cards by Nvidia with Windows 7.