I have an oddball Western Digital. It likes idling well above 50C in my Mystique in the basement, with my intake fan blowing across it. When scouring the drive it used to go above 68C in its original HP Pavilion case... it can still reach 60C now. Definitely scared me and my friends, but hey, the drive still works....
I also have a Maxtor which idles around 40C. Ironically the WD's SMART data scores higher than the Maxtor's in SpeedFan.