This seems backwards...
For a browser anyway:
These efforts have been ongoing since last year and have been extremely successful but we can’t ensure 100% compatibility without your help. We need you to test and ensure your sites, extensions, and applications are ready for IE7. We strongly encourage you to do the following ASAP... (emphasis was original)
Not sure about that (also, I doubt they could ensure 100% compatibility even with our help - which they seem to imply they could... but I digress).
Be nice to let IE6 and IE7 run on the same computer (I know there are hacks to make it sometimes work - but the official answer is virtual PC, not reasonable for most end users). It would be nice if they had a "IE6 mode" (sort of like this Firefox extension gives Firefox an IE6 mode, hmm, wonder if that'll turn into an IE7 mode soon).
Speaking of firebox extensions, Lifehacker pointed me to this one. Very nice, I hit F2 now and I'm editing my asktom answers in gvim instead of a text area, I like that. Very useful.
No, I haven't tested asktom against IE7, no, I probably won't either. We'll just see what happens when this "upgrade" is unleashed against us all "very soon"