It is subjective but I do belive my g260 (not the 55nm one though) is a bit more quiet then my old gainward 8800gt. The 8800gt did not use the reference fan tough pic
. It was a dual slot cooling solution. Fan house was perforated and open on the sides.
With default fan the gtx260 will go up to 50% temperature at that point is around 74c (40% fan at idle 44c)
Be nice to see some input from a 55nm user