In the article Steve Ballmer says that they made the decision to discontinue XP so soon because the vast majority of new computer buyers are choosing Vista.
I've had two days recently where if I could have walked into chain store and gotten a modern laptop with XP on it for circa $1k, I would have. Vista compatibility issues have cost me hours, if not days, of work.
I need to talk with my primary client about trying to move some of their stuff to Vista (It's harder than you'd think), and I'm glad that the chip supplier whose development environment I play with seems happy to support Linux for their tools.
On the other hand, I've billed a few days helping people to make their applications Vista compatible, so if you subscribe to that economic school that believes that vandals breaking windows grow the economy, then I guess it's a good thing...