Windows is too powerful and expensive for most users. In the past, most PC users did not write very much, never edited a photograph, weren't punching numbers into spreadsheets, in short, didn't need the power that has always been available to them, not only in the later versions of windows, but even going back as far as MS-DOS and Windows 3.0.
So what we're seeing, I think, is a settling of the PC market into a core group of users who need the power and interface capabilities of Windows and its wondrous array of software. There are uses relating to business and personal needs that require substantial input of text and that require large screens that even laptops can't handle with convenience. I own a PC, laptop, iPad and smartphone and each of them has its place and importance.
This current shakeout was inevitable and I fault Microsoft for not protecting its interests by unifying interfaces and file types across multiple device types. And that remains the big opportunity for Microsoft. Windows 8 could be made to work on all devices with MS Office available with one subscription for all devices we own.
Apple has won market share by combining features into the iPhone/iPad that satisfy people who don't require PC power and who want portability, the Internet and games. But make no mistake, PC users also want these things AND we want and need our PCs. So Apple and its imitators got all of us but left PC users without standards.
Microsoft has the opportunity to do the same thing for those who must have PCs but also want (and need) portability and standards. They own that whole market! I really wanted a Windows smartphone to work for me because of Office (OneNote, in particular) but the Windows smartphones aren't as good as my BlackBerry Z10. And a "matching" Windows 8 tablet is not really unifying yet, not to a PC and smartphone.
In the end, I think Windows 8 will win by default, but what's really telling to me, and helps explain things, is that despite being on the market for over 30 years, not even robust tasking software (To Do lists with deep features) is available with auto instant synchronizing across all platforms and devices.
Until PC users are regarded as a unique and steadfast market, unification, I guess, won't happen. It's too bad because Microsoft has that to itself if it would just fire 90% of its software developers and then lock an elite bunch of 18-year-olds into a room for a year to get the job done.