The automatic orientation-flipping behavior is provided by a utility that the OEMs provide. Since Windows Vista is not privy to such utilities, you don't have automatic orientation-flipping behavior in Vista.
Unfortunately, you will have to wait for the OEMs to update their utilities, then download and install them to your system, before you get this (admittedly convenient) behavior back in Vista.
--Hilton Locke
Tablet Platform Test
http://blogs.msdn.com/hiltonl/