Itís true that Apple's desktop is ahead of Linux's desktop, and yes it is also true that Apple is developing a presence in the desktop and server market (where Linux has its strength.) But Apple seems poised to continue its exclusionary stance - that is, Apple's Mac OS X will only run on Apple hardware, whether its Intel CPU based or not, and Apple computers will still continue to carry a price premium. If Apple planned to allow users to run Mac OS X on any x86 machines, maybe Linux would be right to be scared. But it seems unlikely and indeed even impossible that Mac OS X will run on anything other than an Apple machine. Linux, on the other hand, runs on any old i386 hardware.
From this vantage point, it looks like the net effect for Apple is going to be break-even at best. I donít think Appleís move spells doom for Linux on the desktop, or poses a serious threat to Linux in the server market, and it certainly doesnít mean that Apple is poised to defeat Microsoft on its home turf.