This is a major harware shift for Apple, but the reasons being stated are that IBM is not keeping up with Apple’s demand for low-power, faster PowerPC processors, especially for the PowerBook notebooks (there still is not a G5 based PowerBook).
Mac OS X has reportedly been developed with two codelines, one PowerPC based and the other, until now unannounced, for Intel based CPUs.
The switch may bring down the price of Macs across the board, but they won’t be able to boast the performance advantage, GHz vs GHz, as they have done in comparison with PowerPC vs Intel chips in the past.
This move also puts an end to any speculation that the IBM/Sony/Toshiba jointly developed PowerPC based ‘Cell’ processor (for the Playstation 3), with multiple processing cores, will ever make it to the Mac.