When Longhorn debuts this october 26th at the Professional Developers Conference in LA it will debut with a whole new theme code-named "Slate". The Longhorn PDC build (4051) was decided around two weeks ago. Since then lucky company employees have had the chance to use the OS or take a look at it but are under strict orders not to talk to anyone about the PDC build.
Two pictures (which are confirmed to be real) have leaked onto the internet showing the new theme. Although they're not the best pictures they do however highlight the new theme very well. The leakers known as "ABSO1ut3 1nfin!ty & B3y0nD" leaked the well documented 4029 screenshots around 2 months ago. Included in the package is a set of Q and A's making people aware that build 4051 is the PDC build, aero isn't included in the PDC build and will only be demo'd and also that plex is no longer the theme, "slate" has replaced it.
Also included is a note to Robert Scoble (http://longhornblogs.com/scobleizer/) documenting how these pictures belong to him. Robert is an MS Employee who has helped manage PDC. According to internal sources at Microsoft the PDC build is "amazing" and very stable. Roll on 26th October :)
Great thanks to ABSO1ut3 1nfin!ty & B3y0nD for these screenshots.
Screenshot: Full Window
Screenshot: Menu Bar
News source: In-House