I just came across this place to register for info on betas via Technet.  It may well be worth signing up.

Since I already run Office 2007 & Windows Vista, I can wholeheartedly say these are great productivity tools.  Exchange 12 has so many fabulous features that I can't wait.  The down side is that Exchange will not ship for SBS until after Windows Server Longhorn, which means we will have several months of Exchange 12 shipping and the only way to add it to an SBS environment is via an additional server, x64 enabled.

http://www.microsoft.com/technet/prodtechnol/beta/preregister.mspx is the link you need to go see.

ttfn

David