This is the best description of the WDK that I've seen in a blog yet. Very cool. Also very cool, most of the site appears to be in Italian. Part of the post appears to be copied directly out of a press release.
"We're very excited about sharing this important milestone for Windows Vista and the WDK. Join the 10,000+ beta testers in the Windows Vista Technical Beta Program, and take this opportunity to test the WDK. And then please, please, please provide feedback to Microsoft, following the procedures described in the Beta 1 documentation. "
That is interesting because, as far as I know, we haven't issued any such statement about the WDK. I'm not saying it is inaccurate, we are very excited to ship Beta 1 of the WDK. No sources are sited for the announcement.