That's not true in all cases--I'm using SpeedFan on my wife's computer to monitor the temperature of the 6800GT GPU and adjust the fan speed appropriately. This was the reason I got SpeedFan in the first place, because the buggy Asus SmartDoctor software for its VGA cards was causing all kinds of problems. If SpeedFan can't monitor your video card temperature, but the nVidia control panel and RivaTuner can, then I don't think you have the latest version of SpeedFan. In any case, I discovered with my 7900GT that neither RivaTuner nor SpeedFan could control the fan speed. I bought an aftermarket cooler to quiet that thing down.