I just received my Gigabyte GTX 280 yesterday. Running it @ 666/2500. With the fan set to 60% it idles @ 42c. With the fan set to 80% it hits low 60's under load in everything I've run (3DM06, FEAR, Stalker, Bioshock, SS2) except Crysis, which goes up to 70c/72c.
At 60%, the fan is inaudible over my other system fans. At 80% I can definitely hear it over my other fans, but I can't hear it while gaming. I supposed that has to do with the five speakers blaring in my ears and trying to stay alive in whichever game I'm playing.
BTW, running @ stock speeds the card was 100% stable with the fan @ 60% for hours of gaming. The only app that went over 70c was Crysis, everything else topped out in the mid 60's. I run the fan @ 80% because of the OC and since it's not noticable to me while gaming. It may be stable even OCed @ 60% fan speed for gaming since....
...folding over night for about 8 hours @ 666/2500 with the fan set to 60% had a flatline in rivatuner @ 64c this morning.
Needless to say, I love this card!