After pronouncing Windows Vista SP1 a "performance dud" two weeks ago, Devil Mountain Software, a Florida-based software development firm, reported that an upcoming update for Windows XP will offer substantial performance gains.
Running an Office productivity test suite on a preview version of Service Pack 3 for Windows XP, Devil Mountain discovered a 10 percent performance boost over the current version of Windows XP, the company reported on its blog.
Source: Yahoo
Not sure if this has been posted already, I did search though.