I took the plunge today -- switched to Vista and Office 2007 for my primary PC (to be precise, I switched to a new PC running Vista and Office 2007 as my primary PC). No problems so far -- Office, Notes R7, FeedDemon, Windows Live Writer, Groove, and other apps I use on a daily basis are working with no problems, and I'm looking forward to working in Word 2007, PowerPoint 2007, etc.
I'm also very impressed with the eval PC I'm using, a Dell XPS M1210 with a couple gig of RAM and a couple more on a USB drive (which Vista exploits for system swap space etc.). The only bummer so far: I can't use Aero mode with the external monitor I'm using with the M1210 (although Aero works fine when I'm using only the laptop display).
I'll post notes here as I gain more experience with Vista and Office 2007.