Microsoft is doing something with Windows 8 that it should have down with Windows 7 and Vista. It's paring down the number of SKUs to just three, one of which is designed for ARM processors, leaving the x86 crowd with just two versions to choose from. Every grade school teacher who has ever taught their students the K.I.S.S. (as in, Keep It Simple, Silly or Stupid) principle should be giving each other vindicated high-fives.
Forget about the gamble Microsoft is taking with the controversial Metro UI overhaul. Simplifying the SKUs is a great thing, and here's how it works. If you're rocking a PC or tablet with a x86 processor, whether it's 32-bit or 64-bit, your options are Windows Pro and just plain Windows 8. For most people, Windows 8 will be the right choice. So, who should consider Windows 8 Pro? Anyone who can benefit from:
BitLocker drive encryption
Domain management and connectivity
None of the versions will ship with Windows Media Center, though it will be offered as an "economical" media pack add-on to Windows 8 Pro.
The other main version of Windows 8 is called Windows RT, previously known as Windows ARM or WOA (Windows on ARM). Windows RT will sport touch-optimized desktop versions of the new Microsoft Word, Excel, PowerPoint, and OneNote.
Finally, let's talk upgrades. Windows 7 Starter, Home Basic, and Home Premium users will be able to perform an in-place upgrade to Windows 8 and Windows 8 Pro without issue. Windows 7 Professional and Ultimate users will only be able to upgrade to Windows 8 Pro; jumping to the plain version of Windows 8 will require a clean install.
More info, including a handy chart outlining all three versions, can found in Microsoft's official blog post here.