I've been a Windows Vista Home user for several years and upgraded to Windows 7 Pro last month because I had read good things about the stability of the new operating system.
Well, I was first surprised that Microsoft didn't like that fact that I wanted to go from Vista Home to 7 Pro, something they call a, "Clean Install" as opposed to a simple "Upgrade".
With an upgrade all of your old programs and data stay put, no backup required.
However when you go from Home to Pro it's a different category called Clean Install. As the name implies you have to re-install all of your old programs, which is just absolutely a hostile way to treat a loyal customer. Why didn't Microsoft plan to allow anyone to upgrade to Windows 7 Pro without a Clean Install?
There is no good technical reason for making me do a clean install and loosing literally hours of my precious time doing something unproductive.
I have to admit that Windows 7 does open faster, close faster, and makes my Outlook 2007 work without crashing (in Vista Home it would crash about every 5th incoming email or so). I also get more "eye candy" and a handful of new applications.
Bottom line, any new PC will have Windows 7 on it, so upgrade only if you love new technology, have envy, or enjoy spending massive amounts of time on your computer.