The secret Apple chip design plan rumors got some new fuel this week when an ATI Chip Designer moved to Apple. The whole idea of Apple planning on designing their own chips started when the company bought PA Semi last year.
It is totally reasonable for Apple, which is holding its own in the high price segment for computers and on the cutting edge for mobile devices to establish a new very powerful differentiator.
If Apple can offer more powerful chips for graphics and processing, that make their products better in some way than other devices that use the currently available chips from Intel, AMD or others, it would offer a huge advantage.
Apple could continue to argue the higher price for their product even easier than today. The Sony PS3 also has a unique chip with the CELL, but Sony is still not able to really leverage this extremely powerful chip. I trust Apple to do a much better job in leveraging unique hardware advantages in the market place.

Reuters carries a feature article looking at the potentially "hurt feelings" of current iPhone chip suppliers like Samsung, Marvell, Broadcom, and Infineon.