Got back safely from L.A. (despite the fires), cured the cold that plagued me during the PDC, and now I (as most oft the PDC attendees, I assume) am playing with the bits which were distributed at the event. Longhorn is fascinating, esp. the XAML stuff. (Hope to get some AERO soon ... :). Of course it's alpha stuff, so some apps (notably explorer.exe) are leaking here and there, but there are infos on the web (see http://220.127.116.11/Chris123NT/PDC_4051/LHGuide.html, e.g.) how to turn that stuff (sidebar - it's pretty useless in this version, anyway) off.
Whidbey is equally fascinating, fast and really stable. Too bad the smart device stuff is only rudimentary and not really usable at this time. (Anyone saw Ori Amiga's talk about the future of NETCF? That's what I'm waiting for!)
Tried a couple of apps on Longhorn to test backward compatibility. Most of the stuff just works, but a few apps refuse to even install since their installer checks for the OS version, sees "6.xx", shakes its head, and says: Dunno this stuff, won't run. (Take Pinnacle Studio 8, for example. Or the DirectX 9.0a installer.)