People moaned in the same way when they tried to install XP on a Celeron 300. The difference back then was that there were clear advantages to getting XP running, cached logons shorted boot time etc.
While I now have Vista running smoothly on an up to date machine, the question still remains "what is the advantage of this OS"?
Artificial factors aside such as making DX10 Vista only, I can think of none.
OSX is not an enterprise alternative. Ubuntu, is not an enterprise alternative. Linux comes in more flavours than even Vista.
The solution would be XP's software catalog and enterprise features, OSX's ease of program use (DWG files) and linux's security.
Or OSX with Active Directory :p