And what was the last x86 CPU that could run without a large (more than 3cm^2) cooler and fan? 266 MHz Pentium 2?
Heat and power are the only real advantages PPC have over x86 chips. What other reason for switching? Ok, I'm jumping to conclusions again: nobody said it was a PPC chip. But do IBM have any chips close to being as powerful as the PPC range? I don't know of any x86-compatible ones since Cyrix, and that died at the 300MHz or so along with the P2.