If you plan to use VS 2008 with SourceSafe, make sure to pick up the Update CTP too.  Without it, some features like “Open from Source Control” will not work at all.  Pay close attention to the install instructions as well.  As it says in the KB article:

You may receive error messages when you use Visual Studio 2008. This problem occurs because some compatibility fixes require the Tdnamespaceextension.dll file to be reregistered after you install Visual Studio 2008. To reregister the Tdnamespaceextension.dll file, type the following command at the [elevated - RB] command prompt:

regsvr32 “%programfiles%\Microsoft Visual SourceSafe\tdnamespaceextension.dll”

Full post: Richard Berg’s