I know, it seems like a silly question - it's CPU temperature (as one would assume). However, I am not so sure anymore. The $1799 question remains - did they proposed solutions (Coolbook, excess thermo paste) actually serve to help with the noisy fan issue? I have 2 questions I want to ask everyone: 1) At what CPU temp does your fan kicks up from 2500 to 6000+ rpm? For my MBA, sometimes it's low 50s, sometimes 60s (degrees C). I am running Coolbook, but it really doesn't do much in cooling the computer at light/regular load. 2) According to iStat, what is the temp difference between your cpu and heatsink? My MBA just went through the "excess thermo compound removal" surgery. My heatsink temp reads 4-6 C lower than the cpu now. I didn't pay attention to what it was before, so I'm curious what yours read.