@ Robert Hill
"""Simply put, Intel's adoption of the Core architecture (i.e., the upgraded Pentium-M from their mobile business!) finally made Intel a serious player in watts per processing power. Apple realized that Motorola just could not compete in that space, and frankly the PowerPC architecture was never really aimed at mobile platforms. """
Actually Apple stopped using Moto chips a hell of a long time ago. They moved to IBM chips at some point that you can look up on Wikipedia. And IBM did have a low power laptop chip out in plenty of time for Apple to start using it in their laptops, they just claimed it was too complex (or they were already dealing with Intel.) The PPC architecture doesn't have any innate limits on the power consumption (Look at PA Semi's stuff,) an architecture isn't a lot more than an instruction set, which can be implemented many different ways.
"""Considering that Apple sells a very high percentage of laptops, and even their desktop solutions are known for attempting to be quiet and unobtrusive, power efficiency was just too important for them to pass up, even at the cost of re-writing and porting all of their software and facilitating 3d parties to do so."""
They were actually designing OS X with x86 in mind for years. The porting wasn't a huge problem at all. Plus they emulate PPC reasonably well, so very little previously functional software broke.
The real reason they went with x86 is because Intel chips are cheap. Really cheap. IBM kept jacking up the prices for Apple, supposedly because Apple was such a terrible company to do business with. Apple can now sell a fastish (obviously not Power6 fast) set of computers for roughly the same price that they sold the PPC kit for, but using cheap CPUs and more or less pre-made motherboards and things. They must be laughing their asses off that they can sell a macbook for a $300 markup over a Thinkpad of similar spec.
If they had stuck with PPC, they could have had extremely low power and fast laptop chips, plus been the only company to put Power6 into a desktop. Sure it'd require some of their custom liquid cooling and all that, but at the very least a 5GHz sticker would sell a lot of machines, plus they would probably be quite fast.
And if they weren't essentially the same stuff I already have I might actually want to own one.