If you receive the below error when trying to build a project that was composed using the VS 2008 Beta, you need to modify your config files.
Change the assembly version from 2.0.0.0 to
Version=3.5.0.0
Error 1 Could not load file or assembly 'System.Data.DataSetExtensions, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' or one of its dependencies. The system cannot find the file specified.