Hi Roger,
I would also like to mention that to make Windows Vista as standard OS across the business, many businesses would like to go through a testing procedures for many of their production applications which I think will take awhile.
It may sound really strange to you but its true that I have seeing many businesses have 3-5% of their network still running Windows 98. As Vista has fewer vulnerabilities which means less patch management.
I would really like to see businesses along with home users considering migrating Windows Vista. Likewise, testing and making sure Windows Vista is stable with other applications they need is really very important which I think will take a little while.
Cheers
Shoaib