Microsoft won’t let you a easy upgrade on Vista this time, but this might be the factor for people who want to upgrade or not. If you buy a Vista upgrade CD’s for you Xp machine, Vista will invalidate your Xp license key(so no dual-boot nor you will be able to use that use that Xp on a different PC.

Your woes won’t end their if you ever think Vista isn’t for you and decide to uninstall Vista, you won’t be able to revert back with your Xp Cd anymore. If Microsoft doesn’t change this upgradation policy soon enough, sooner or later they might get sued by a unhappy customer.