As far as stability testing goes, I let ATITool do its artifact scanning for 12 hours the other day... BOY did the power brick ever get hot, lol. Besides that just general gaming and such has been flawless.
Temps in games (or should I say the games I have) are decent. After playing F.E.A.R. for 3 hours straight I hit 81C (peak) and never had so much as a stutter. The only other game I have installed right now is GTA San Andreas, and it doesnt really push the GPU much at all, as I top out around 72C.
Third, NO I don't run the fans on high all the time. I have a nice fan profile setup with I8k, where they run on slow all the time. If I turn the fans off TOTALLY, the temps hit 60C and stay there (+ or - depending on ambient) and on slow it idles at 50 just fine.