One of these days MS is going to "get it" in terms of what convenience means to customers. Sadly that day will not be the Windows 7 launch
Microsoft's focus has been security and stability. Everything was conveniece first intially. Then they realized what happens when you build a home and leave all the doors open expecting people to close them on their own.
If you do a full clean reinstall, they are sure that the files they want are there with the right versions, permissions, and links. I can see where they are coming from.
That said, I wouldn't mind an upgrade option. That's kinda keeping me from upgrading my main machine at home.
Then again, at work I just decommissioned a VMWare ESX server with 4GB of RAM and two opteron processors. Sounds like it's time to install win7 on that and make it my primary machine.