Hot...
Idling and typing (FireFox only app really running) iStat says:
HD: 57C
CPU(s): 42
AirPort:63 (I'm wireless 30' from Access Point).
Ambient: 25
GPU diode: 59
...
Pwr Supply: 75
Your HardDrive will last longer if it is cooler. Better temps would be 50 and below. I suspect the Intel CPU spec is the temp of the burried Floating Point processor where much of the heat is. External temp to achieve 100C at that point may be as low as 80C; I would target 80C as the firewall.
Better temps for CPU/GPU are in the low 60s; 65C or less with 68C pushing it.
When chips get hot, the metal inside literally moves. It is called Electron Migration. This is possibly the leading cause of chip failure over time. All chips have *some* electron migration. Intel designed the 386 with a 40 year life based on electron migration at normal operation, to guarantee a *10* year lifespan. Heat things up and you'll be lucky to get 5. Yes, the chip has been surpassed by then, but just try and replace your iMac CPU or GPU and I don't think many people would do it... My wife's MacPro lasted 6 years. Would have lasted longer had it stayed cooler; the South is Hot. I give my iMac 3 years tops if I don't speed up the fans.
(fans idling at 600, 1200, 1200 as always... I think I saw 1900RPM, once.)
Who knows, maybe my controller is bad? However, the fans do pickup, but only when the CPU gets very hot. It seems to ignore GPU and PS and AP...