IMHO, there is little reason to buy the full (non-upgrade) versions of Windows Vista, unless you don't have a legitimate copy of Windows 2000 or Windows XP.
On the other hand, installing from an upgrade disk onto an empty hard drive is slightly more complicated than from a full, non-upgrade install disk: You must provide a legit installation/setup disk from Windows 2000 or XP in order for the setup program on the upgrade to verify your copy.
With all that said, here are the full MSRP's (in the US) of all of the editions of Windows Vista:
- Ultimate (non-upgrade), $399.95
- Ultimate (upgrade), $259.95
- Business (non-upgrade), $299.95
- Business (upgrade), $199.95
- Home Premium (non-upgrade), $239.95
- Home Premium (upgrade), $159.95
- Home Basic (non-upgrade), $199.95
- Home Basic (upgrade), $99.95
For most power home users, I'd recommend the Home Premium edition rather than the other editions, since it provides the best value in the group. Of the others, I'd only recommend the Home Basic edition if your PC either has a slow, sub-2GHz-class CPU or an old or slow graphics subsystem. And the Ultimate Edition is nice to have, but not entirely essential, IMHO.
Even at that, I'd still hold off on such an operating-system upgrade until at least the first service pack for Vista is released.