when im using the gps and it gets warm i just blast the a/c and hold the phone to the vent to cool it off
i used the GPS last night for about 30-40 minutes and at the same time was streaming music using DroidLive. half the time the phone was plugged in to my charger, and once it was up to 100% i unplugged it from the charger. when plugged in my cpu is clocked at 550mhz, and when it's unplugged it's overclocked to 1ghz. not at any point was it hot. i think my cpu reached a max of 42, maybe 45, i don't remember exactly, but it was never anywhere near a number that concerned me.