I bought the 2.5 GHz model on Thursday and installed FanControl. Now I don't want to use it anymore and monitor the temperatures and fan speed a bit. I think I uninstalled it correctly yesterday and did the SMC reset. The fan speed goes down to around 1.800 rpm and stays there if I use Chrome and a few other light apps only. The CPU temperature is at about 52° Celsius. My questions is: When does your fan spin so fast, that the temperature goes down? I tried to watch a YouTube 1080p clip yesterday in fullscreen, I exited when I thought that the fan speed reached about 5000 rpm and the CPU was at 70° Celsius at that moment according to iStats. At that time it cooled down to about 53° again while the fan spinned slower and slower. I'd like the fan to not spin that fast and keep a temperature of 65°-70° even under load, is that possible somehow? When I play Source games, which are pretty CPU intensive, the fan spins really fast (5000 rpm I believe) and sounds like a little jet engine 
In regards to your iStats problem, in my Dashboard it does not show the CPU jumps you mention. Do you use Lion 10.7.1?
In regards to your iStats problem, in my Dashboard it does not show the CPU jumps you mention. Do you use Lion 10.7.1?