Aaron Stebner's WebLog provides a fix for those of us with beta one and other builds of Whidbey who get package load errors when trying to install beta two. Nick found this out this morning and passed on to test to confirm. From Aaron's site we see:
The VS 2005 beta cleanup tool is an automated tool that is designed to resolve common issues seen by customers while trying to uninstall VS 2005 and .NET Framework beta 1 or Community Tech Previews (CTPs) and install VS 2005 and .NET Framework beta 2. It automates the officially published uninstall steps for Express Editions and for other versions of VS. It also automates cleanup of various files and registry keys that are known to cause problems if beta 1 or a CTP has already been uninstalled in a different order different than the uninstall steps describe.