When you're gaming the game would run on one screen, and whatever else you have on your desktop will be on the other screen. When no gaming you can drag applications across both monitors as if they were one. You'll love it, I'm sure.
What he said. I'm currently running 4 monitors, 20" samsung 204b LCD, 15" LCD and dual Proview 17" CRTs, on a 8800gts and 7300le(2 monitors on each card). i love it