Anand from AnandTech compared the old iMac G5 with the new Intel-based iMac Core Duo:
Now that Intel's Core Duo has finally been launched, Apple could go ahead with their PowerPC to x86 transition, but there's another problem. A very smart man at Intel once told me that you should never launch a new microarchitecture alongside a new manufacturing process, with so many variables things are bound to go wrong making delays inevitable. With the Core Duo, Intel not only introduced a reasonably sized change in microarchitecture, they also made the shift to 65nm on this semi-new architecture. The end result seems to be that availability of Core Duo processors and chipsets just isn't all that great..