I have an 20" Intel iMac running 10.4.6 with 2gb ram. I have been using CoreDuoTemp to monitor my temps. 43C is the highest temperature I have seen when quickly scrolling through my iPhoto library. According to MenuMeters, both of my processors were pegged at 100%. During this little test, very little heat was escaping from the top vent. I'm not complaining! It runs significantly cooler than the G5 iMacs I had. The temperature in my apt. is around 19C.