Microsoft officially announced today the different Windows Vista packages, after they have leaked a week ago on their site.

Get ready to distinguish 6 Windows Vista versions: Windows Vista Business, Windows Vista Enterprise, Windows Vista Home Basic, Windows Vista Home Premium, Windows Vista Ultimate and Windows Vista Starter.

The only two interesting packages for power users are the Windows Vista Home Premium and Windows Vista Ultimate.
Windows Vista Ultimate has all entertainment features, mobility features and business-oriented features available in Windows Vista.
The Windows Aero UI is available in Windows Vista Home Premium and Windows Vista Ultimate.
So it is a matter of pricing, if by default every power user is anyway just buying Windows Vista Ultimate.
More details in this Microsoft press-release.