I got my iMac in March this year, it's a 20" 2.4GHz Core 2 Duo, the final one before the March refresh.
It comes with a Western Digital Hard Drive, serial number "WDC WD2500AAJS-40VWA1", according to the System Profiler. Does anyone know which model of Western Digital this is?
My iMac does get very warm at times, especially on the top left corner when looking at the system front on.
Checking iStat Pro however, the Hard Drive is showing a temperature of 112F, so everything seems fine with regards to temperature. I had also read that the aluminum case of the iMac actually acts as a heat absorber, taking internal heat away from components, although how accurate that is is questionable.
The only thing about the Western Digital drive, that maybe other users can confirm, is the "style" of accessing noise it makes .... it's as if it makes a low humming as well as a "chirping" noise while accessing. Nothing sounds "out of place", but it's not as clunky sounding as old PC hard drives I've used.