I just upgraded my Windows Vista Business 64-bit to Windows 7 Ultimate 64-bit. I made some screenshots of the upgrade. It took a long time (between 3 and 4 hours, on an HP notebook with an Intel Core Duo CPU T8300 2.40 GHz with 4GB RAM), but besides from the time it took, it went more or less smooth. I only had to uninstall an unsupported McAfee VirusScan (and replace with another antivirus product); the rest were minor compatibility issues.
I downloaded the Technet DVD ISO file, requested a key, and burned the DVD. Then from within Vista started setup.exe.
Most of the time when you are already running Vista you won’t have that much compatibility problems, so I skipped the compatibility check, and clicked Install now.