A major change that would seem totally crazy in the Windows world, but that isn't that much a problem here.
Why so? Well, Apple already switched from 68k to PowerPC processors 11 years ago. At that time, I had a
Macintosh SE and bought a
PowerMac 7200. The transition was painless because of "fat binaries" containing the code for several architectures and a smart emulator which was using just in time compilation long before Java.
Then in 2001 Apple changed their operating system to MacOS X. Again a smooth transition thanks to the "classic" environment (a MacOS 9 sandbox).
So after having changed the heart, then the brain, Apple is changing the heart again. Being able to evolve and adapt to the environment is key to survive.
This move is certainly primarily motivated by laptops for which IBM isn't able to provide low-consumption G5s. So the first Intel-powered Macs are very likely to be Centrino laptops, with enhanced processing power and longer battery autonomy (the first PowerBooks were fairly good at these but where outrun by PCs).
Now the question is who will buy a PowerPC Mac now? For sure I won't, except if their price becomes really interesting...