ComputerWorld comment on a research study by Relevantive which compares the usability of Linux and Windows XP, with XP slightly ahead.
The study looked at how easily two groups of users could perform tasks using the two different operating systems by performing tasks such as creating and administrating files, copying CDs and basic office tasks, such as composing a text and sending e-mail.
A copy of the research study is available in English and German and a forum has been setup for further comment.
Slashdot have also some interesting comments by users in a related post.