Apple dominates the $1000+ notebook sector, in sales done through physical stores such as Best Buy, etc. They have around 91% market share in this area.
PC desktops aren't doing well (across the board.) Consumers seem to be going for power and portability. Notebooks. And really, who can blame them.
Record Mac sales this past quarter is another factor, and this isn't the first out of 19 quarters that they've posted record Mac sales. Most of Apple's revenue in general is generated from Mac sales to begin with. Apple's really the only one that runs a profitable computer business these days. Most of it occurs at the Premium end of the retail pyramid - the top.
Chances are, if you're the average consumer that fits Apple's demographic, which means you've got the cash for it, you'll be seriously considering a Mac. Baldmer has already admitted as much recently, publicly. And MS didn't come out looking the better for it, either. Stagnation and late, derivative product rollouts have been the order of the day in Redmond since XP's release. But hey, licensing your back-asswards imitation of OS X to everyone and their dog pays off. The question is for how long.