The build stamp is 6.0.4051.0 (idx02.031001-1340) for the new Longhorn release. Activation along with a new CD-Key is of course required. The CD-Key that was used for previous builds no longer works, and currently there isn't a new key available. More likely than not keys will be leaked on Monday when PDC attendees get this build on DVD.

Screenshots
SETUP
Setup Screen | Welcome to Windows Setup | CD Key Entry | Setup Type Selection | Setup File Copy

DESKTOP
Default Desktop Wallpaper | Expanded Clock | Windows Version | Internet Explorer | IE Download Dialog


SOURCE