Buck, by all reports, XP is a very stable O/S. It is when you get into the privacy issues that it falls apart (my opinion also), but that can be tightened up with a good firewall, and by NOT using Micro$hafts Passport program. That is an affront to everyone, and a direct attack upon your privacy in itself.
Upgrades? The average user won't be doing upgrades to their computers, they will run the same thing until forced to buy or upgrade due to incompatibilities between software and hardware. XP is built so that anything past a year or two in age is NOT compatible with it, hence a new computer OR upgrade your existing computer to be compliant. Any failing part...and new computers have that problem as well...necessitates re-initing your software through Micro$haft...(pain in hiney). The new Office XP has been known to come up with the message that the machine that it is started on, is NOT the machine it was originally installed on.
??? same machine, just a few weeks older...but still left user w/o program to use UNTIL Re-Initing with Micro$haft. IF a person wishes to use XP, I would suggest give it a year before trying...give M$ a chance to eliminate some of the bugs.
Personally, all my machines are slowly moving away from Windows in any form. It's just a matter of time until the family is all up to speed with Mandrake Linux.