Linux is a good fit for many embedded applications. The economics of the situation make it a good investment to get the configuration/setup/etc. issues just right, because there will be thousands of identical copies put into production.
The desktop has completely different economics. The variation in systems, processors, peripherals, and, perhaps most importantly, levels of users mean that configuration must be both flexible and easy. That's hard to do, and it takes lots of time and money to do it right. Linux nibbles away at that, but Microsoft and Apple have a huge stake in continuing to do a better and better job there. So it is not at all clear that Linux can close that gap, because it's not obvious who will invest the money to do so. Even the head of Redhat says home users should just use Windows XP.
Servers are in-between. More variation than embedded, but less than desktop. A higher level of proficiency in users. So Linux can be competitive there, but so can Microsoft and others. Microsoft's strengths are in the small to mid-size company that doesn't really want to have a full-time IT staff, and companies that need very leading edge capabilities. Linux does better when a company expects to use lots of servers, but doesn't need them to be leading edge on technology like Web Services, or use lots of weird peripherals.
There's room for both. It continues to astonish me that Linux partisans sound like religious zealots in promoting their case. Technology is just a tool, folks. You use the tool that works best for you, and let the other guy do the same. And sometimes, any one of several tools will do the job.
I'm not so sure that the level of proficiency required to police the security of XP as a multiuser home platform isn't approaching, or even exceeding, that required to install/maintain a recent release of Linux. It's at least getting to be near the same ballpark.
XP SP2 might change that but I'm beginning to think Windows might be a fatally flawed design with depth of the imbedded browser.
Great post.
"So it is not at all clear that Linux can close that gap"
Time is on Linux side. It has become obvious that there are only a finite amount of things left to do to the desktop that make any difference to the end user. After that, it is only a matter of time for Linux and FreeBSD to catch up. Longhorn is the last hurrah for Microsoft, mostly useless bloatware.