Hold your horses, vaquero. Let's not blow this all out of proportion here. While it's no secret that a certain amount of Vista purchasers are utilizing that "downgrade to XP" option to its fullest extent, a small (and let us emphasize "small") collection of data suggests that some 35% of "mainly enterprise-class users" have opted for XP over Vista on their newly-purchased rig. By scouring data from the 3,000 or so members feeding information to the InfoWorld Windows Sentinel tool, the site found that just over 1 in 3 users had defected to Microsoft's previous OS. Granted, the tool cannot take into account Linux users or even the "Hackintosh crowd," though as Randall Kennedy puts it, 35% is "still a huge percentage, and way out of proportion for even the dramatically unpopular Windows Vista."
Update: The author of our source here has seen been released from InfoWorld due to breach of trust. InfoWorld maintains that Randall C. Kennedy's "insight and analysis [is believed] to be accurate and reliable."