From ZDNet:

The sales outpaced the first month's tally for Windows 2000 [...] Commercial revenue from Vista in December was 62.5 percent above that racked up by Windows 2000 in March 2000, its first month after launch.

The marketing muscle behind the consumer launch should allow Vista sales to businesses to start eclipsing what Microsoft saw with Windows XP.

"Sometime after January 30, when Microsoft makes Vista available to the general public and ratchets up the marketing campaign, I suspect that we will likely see sales of Vista in the commercial channel begin to meet or surpass levels previously set by XP," Swenson said.

Well that's encouraging.