My bad. Bad info from this website: Fastest Processor - Cell Phones Top List

According to Wikipedia, the Original & 3G both had Samsung 32-bit RISC ARM 1176JZ(F)-S v1.0 620 MHz underclocked to 412 MHz while the 3GS has an ARM Cortex-A8 833 MHz underclocked to 600 MHz.

I didn't know the 3G was also underclocked.

I still don't see what the concern is about over the 3GS's CPU. Every PDA phone I ever owned rose in temperature through voice use, as opposed to processor use. With both my past Treo phones and my current HTC Touch Pro, I could surf the internet for hours without the phone getting hot, but a 1 hour conversation turns the cellphone into a live charcoal briquet. The solution has always been bigger capacity batteries to decrease resistance.

Wouldn't that be the same scenario for iPhone heat issues?