I originally tried to swap out one of my 200 series cards (using the the newest drivers) and reboot with a GTX 470 in its place. That was a disaster. Didn't realize that the 470/480 had specific drivers different from the 200 series.
Additionally, I know that if you are playing around with clock settings and 'crash' the driver, windows will 'recover' according to itself. At that point, your performance will be ruined until you reboot.