Over at You Had Me At EHLO, Cathy has published the updated documentation links for Exchange 2007 Service Pack 1. There is a lot of new stuff coming, and the new features address pretty much all the issues that clients have raised and will let us roll out Exchange 2007 where we previously faced resistance or felt we ought to hold off on an upgrade.
Exchange 2007 Service Pack 1 Documentation
I got to spend a lot of time at TechEd with Cathy and with a few folks from the documentation team, they have really outdone themselves when it comes to documenting this product.