Go watch, download, whatever, it's good stuff: http://msdn.microsoft.com/theshow/episode041/default.asp
I didn't attend many WinFS-related sessions at the PDC ('cos there was only one of me to go around, and so much to see...and after all, it's a way off still), but I remember that it made a few little lights tentatively go off in my brain (flicker weakly, that sort of thing).
It was good to see some concrete coding examples on the .NET Show presentation, for the first time that really gave me a decent feel for how we would interact with WinFS at code level. I think it would be a good idea for people to review some of their use of Active Directory when Longhorn hits, particularly with the ability of WinFS to perform queries spanning multiple machines (I think I understood that bit correctly).
If only I had a machine that would run (or even install) the PDC build of Longhorn. Sob.Grizzle grizzle.