Jim talks about the importance of componentization, why Windows XP SP2 was a service pack, and other thoughts on things that have been going on during the development of Windows Vista. Check out the first part of the interview here.
One bit that I found interesting was his mention of all the releases that have occurred since the first release of Windows XP - the Tablet editions, Windows Server 2003, Media Center (just to name some that I've used)... I guess they didn't have the thunder that Windows Vista will have. Still, there was a lot of work put into them - I've worked with the Tablet team in the past, and they truly have delivered a lot of improvements.