Just upgraded Vista Ultimate to Windows 7 Ultimate...simples, but took a while.
I had to uninstall my video drivers, AV and Firewall because I was asked too, then it was just a case of run the setup and wait...and wait...
Oh, you can only upgrade Vista xx edition to Win7 xx edition - Home Basic to Home Basic, Ultimate to Ultimate etc. Like for like.
but it's all shiny and new again now and after reinstalling AV, Firewall and video drivers, nothing seems amiss. Don't often like to give them credit, but Microsoft have done a good job on the upgrade routines.