I've also installed Office 07 and a couple other apps and things seem to be running without any issues. And I have the same experience as Martin describes in his blog. Apps open a lot faster in Windows 7. Outlook opens like lightning, and so does Visual Studio. The difference between the two OSes is like night and day where performance is concerned. Now that I've proven the concept, I'm going to back up all my stuff one last time and do a full fresh install on my main partition.
Now the big question is had I had Katmai on SP1 to begin with would it still have shot up the warning on my Windows 7 upgrade? I don't know, and at this point I don't really care.
So that's all I have to report. Katmai and Visual Studio 08 both work just fine on Windows 7. You'll be very pleased with the performance.