Microsoft is showing off Longhorn this week at WinHec. But they're asking users to not show screenshots of Build 5048 in screenshots on websites. Our friends at Neowin and other sites have been asked by Microsoft not to show such screenshots (the EULA for 5048 indicates that you won't put up screenshots).
So what's the deal? Well there's a lot of speculation. Lockergnome's Chris Prillo put it bluntly - "It looks like ass." as the reasoning MS doesn't want it out there. 5048 doesn't have the DWM enabled by default and when it is enabled, it's quite pokey, even on good hardware right now. Bear in mind, this is pre-beta stuff.