Increasingly so. Microsoft licensing makes it so there's no difference to the Vendor what they ship with the machine, and most of them would rather be able to advertise the latest and *ahem* "greatest" OS. Some of them will honor a request to ship with XP even if they sell with Vista, makes no difference to them; it's allowed under the EULA, and the maker is getting paid either way. Dell has been doing this, so if you need to get a machine with XP in the near future, go ask them about it.

Fortunately, it's still very easy to get computers that run other excellent operating systems. Of course, with a Mac laptop at home and a Dell laptop with Ubuntu at work, I _might_ be biased.