Using the MS RTM W7 I upgraded my Vista Business and it went well. Much faster than Vista and reliable.
Then I came across an XP Pro Laptop (1gb memory, integrated ATI graphics). I did not fancy the clean install so I did in-place upgrade to Vista Business (I had a DVD hanging around). I did not activate Vista. I then did in-place upgrade to Windows 7 Pro. Yes it was slow, but mostly unattended. Works a treat!

Tried it again on a Dell Desktop, same method. Please note both starter PC's were degunged first!

Best of luck.

PS, Sadly W7 slows down after a week or 2.