Microsoft has always been, um, "creative" when it comes to its decisions to break up and market the different versions of Windows. Windows XP was pretty straightforward. Except for special editions of Windows that were released as a result of litigation or court proceedings--such as Windows XP Starter Edition for developing markets, and Windows XP Edition N released in Europe (the "N" was for "Not with Media Player"), Microsoft made it easy for most of us with just two versions: Windows XP Home and Windows XP Professional.
Windows Vista editions weren't as clear cut. Vista was released in five different editions: Home Basic, Home Premium, Ultimate, Business, and Enterprise. Coming off the simplicity of Windows XP editions, no one could keep them straight. Windows 7 also came in five versions: Starter, Home Basic, Home Premium, Professional, Enterprise, and Ultimate. The Starter and Home Basic versions were stripped down and often installed on value-based hardware. These stripped-down editions didn't fulfill their missions very well as that hardware could run the higher end editions, and could (mostly) do so without a performance hit. Some features, such as Windows 7 Ultimate's Media Center, were the exception.
Microsoft is taking a straightforward Windows XP approach with Windows 8. For Intel and compatible 32-bit and 64-bit hardware, there will be two versions: Windows 8 and Windows 8 Professional. Windows 8 is the edition that most everyone will use. It replaces Windows 7 Home Premium and includes the ability to switch languages on the fly, which was previously only available in Windows 7 Enterprise or Ultimate.
Windows 8 Pro adds BitLocker and Encrypting File System support. It also has client Hyper-V virtualization and the ability to boot from a virtual hard drive (VHD). Windows 8 Pro is also the edition you're most likely to see in the enterprise, as it also allows you to join a Windows domain, and contains support for group policies and Remote Desktop host. Currently, these features are only available in Windows 7 Ultimate or Enterprise.
Both Windows 8 and Windows 8 Pro will be installed at the factory, and will be available at retail locations. They will be the only editions available at retail. There will be some specialized versions available via corporate sales channels. For example, Windows 8 Enterprise will only be available to corporate customers with Software Assurance agreements.
Windows on ARM, or WOA, will be branded as Windows RT. It won't carry the Windows 8 brand, even though it has most of the same features and is built on the Windows 8 code base. It will only be made available on ARM-based computing devices and only via factory install. It will not be available for direct purchase.
Pricing for all Windows 8 editions has yet to be announced.
Although Microsoft might have a better handle on marketing its latest OS editions, we'll have to see how the unfinished OS finally turns out. In my review of the Windows 8 Consumer Preview, I found that the tablet-based experience was wonderful. My examination of the Metro UI showed that it works very well on tablets and mobile devices. The new Metro Apps were interesting, and should also work well on the same hardware. I have my doubts, however, about the desktop experience.