Most of us Linux enthusiasts don't care about the processor if our apps are available and we get adequate performance.  And the Power series, being RISC, is not as vulerable to scaling factors as the intel based architectures - IBM could well be making this play with some technical knowhow and prowess for which even Microsoft can't compensate

In one fell swoop they cut their ties to Microsoft, obtain hardware and licenses to hardware upon which Linux runs, get a recognised smooth desktop, and a respected if small consumer market channel.

This also makes sense from the point of view that IBM wanted to challenge MS and their intent to buy Sun (as long standing rumor had had it) was thwarted by Sun's sweetheart deal cum poison pill with Microsoft.

Bringing the market for their chip in house and eliminating licensing costs should allow them to sell the Apple hardware cheaper than Apple can, and by switching the OS to Linux they can consolidate much of the OS development and support costs with their ongoing Linux development.  By open-sourcing the desktop components they will simultaneously gain added good will from the community and gain the open-source synergy in its development.

The questions remaining are whether IBM can capitalize the small Apple consumer marketing channel into a corporate marketing channel, and can they make the price competitive with commodity intel architecture as the Linux desktop grows in popularity.