One thing that I did not see the answer to was Confused's post "How does registration work with 2 PC's at home?" I always thought you could install software with a single license on any computer that you routinely use
Demosthenes, what you (and a lot of others) thought and what the license agreement said were two different things. What MS does with the new version of Windows is enforce the license agreement by making you pay for a separate copy of XP for each machine. You can pay $99 for your first upgrade and about $89 for each of your other upgrades up to (as I recall) 5 machines.
Because many of the people who have been "pirating" for home use all these years have been tweakers, professionals, and other opinion makers who have often promoted Microsoft software to businesses and casual users, and those people will now have a greater incentive to look at Linux and other open source OS's, I happen to think MS is being foolish, but that its legal right.