Seems like windows users will have a lot of choice and sysadmins a lot of headache. According to Paul Thurrott’s Supersite for Windows, there will be at least 8 different versions of windows vista.
Windows Starter 2007: Aimed at beginner computer users in emerging markets who can only afford a low cost PC. As with the XP version, Windows Starter 2007 (note that it’s not branded as Window Vista) is a subset of Vista Home Basic, and will ship in a 32-bit version only (no 64-bit x64 version). Starter 2007 is analogous to XP Starter Edition. This version will only be sold in emerging markets.
Windows Vista Home Basic: A simple version of Windows Vista that is aimed at single PC homes. Windows Vista Home Basic is roughly analogous to Windows XP Home Edition
Windows Vista Home Premium: Whole home entertainment and personal productivity throughout the home and on the go. Windows Vista Premium is similar to XP Media Center Edition, except that it adds numerous other features and functionality, including Tablet PC support.
Windows Vista BUsiness: A powerful, reliable and secure OS for businesses of all sizes. Windows Vista Business is roughly analogous to XP Pro today. This version is aimed at business decision makers and IT managers and generalists.
Windows Vista Small Business: Designed for small businesses without IT staff.
Windows Vista Enterprise: Optimized for the enterprise, this version will be a true superset of Windows Vista Business.
Windows Vista Ultimate: The best operating system ever offered for a personal PC, optimized for the individual. Windows Vista Ultimate is a superset of both Vista Home Premium and Vista Business., so it includes all of the features of both of those product versions, plus adds Game Performance Tweaker with integrated gaming experiences, a Podcast creation utility (under consideration, may be cut from product), and online “Club” services (exclusive access to music, movies, services and preferred customer care) and other offerings (also under consideration, may be cut from product).
N Editions: Windows Vista for the European market, in order to meet the requirements of an antitrust ruling there. Windows Vista N Editions–Vista Home N and Vista Business N–will mirror the Vista Home Basic and Vista Business versions, respectively, but will not include Windows Media Player and other media-related functionality.
There’s whole lot of detail in Windows Vista Product Editions Preview