I wanted to do a quick post as to why this makes a whole lotta sense on Apple's part.

A couple years ago, Apple was pretty close to shifting over to Intel. Instead, it decided to place it's bets with the G5, hoping that IBM would deliver. IBM hasn't, and Apple is probably getting tired of having to liquid cool or otherwise come up with clever cooling solutions for its product. Apple's shift to Intel is also probably a clear signal that IBM isn't anywhere close to delivering the oft-desired G5 PowerBook, which brings up (perhaps) the most important statistic:

53% of computer sales last month were laptops

The Apple laptop line, in terms of performance, has stagnated due to a lack of a top-of-the-line processor -- iLife applications like iPhoto and Garageband seriously suffer.

Apple does have to suffer the inevitable price comparisons, but the net effect should be that Apple nullifies hardware as a major purchase decision point (one they were losing on), which will leave a purely software comparison -- given the Longhorn screenshots I've seen, Apple is likely to do quite well if that's how they can get buyers to choose.