Here is my personal view of why Microsoft made Windows 8 the way it is, and where they might be heading. I'm expecting I've got one or two details wrong, but bear with me.
Mods, apologies if this is in the wrong section; feel free to move it to the "Windows 8-related Rants and Essays" section of the Forum or whatever .
Once upon a time, computers were pretty rare beasts. Only real specialists used them for specific tasks. As time went on, mainframe computers started to be more common, and a new type of job emerged as more and more people had a job "working in computers". But computing still wasn't part of everyday life.
Then came the "Personal Computer". These started to become widespread in business, and people who had other jobs that weren't just about using computers started to do more and more on PCs; things like word processing and spreadsheets. Some people also had home computers, which I suspect tended to be used mainly for games.
Fast forward a little more, and the internet became widespread. And suddenly, ordinary members of the public who hadn't been interested in computers or playing games up to now found a reason to get a computer for home use.
At one point, Microsoft had two separate branches of operating system releases; for instance Windows ME and Windows 2000. Both were designed for the non-technical user rather than a server adminstrator, but had different code bases. Roughly speaking, Windows ME was for use at home (well, if you could stand it, anyway), and Windows 2000 was for use at work. But then the user-focussed operating systems got merged into Windows XP, with Windows Server products continuing for the server types.
And it's got to the point where lots of people (including myself) spend hours a day at work using a computer, even though I'm not in an IT role. Also, computers got used by students at school/ college/ university.
But now we have tablets. And I strongly suspect that those ordinary members of the public who didn't really want to use a computer in the first place, but liked the access it gave them to the internet etc, are finding that a tablet as a personal device is as much of a computer as they need. Because they weren't really interested in using the computer, and don't spend all their time on one, they just like a subset of the functionality a computer previously gave them, and find that tablets now do that job.
I heard an interview the other day with someone from PC World/Currys (pretty much the sole surviving big chain of electrical bricks-and-mortar stores here in the UK) saying that a big reason they made a profit last quarter was people buying tablets.
So (to finally bring my story to Windows 8!) I can entirely understand why Microsoft wanted to bring tablet-friendly functionality to a new version of Windows. It's where a lot of money is at the moment. And I guess they at some point considered whether to branch off a separate operating system (back to the days of Windows ME and 2000) or to keep them together. I guess they sort of did the branching thing, with Windows RT, but there is some evidence that the code base of Windows RT and Windows 8 isn't all that different. (Windows RT jailbreak smash: Run ANY app on Surface slabs ? The Register)
Windows 8 is a compromise; it does most of the things in previous versions, adds the tablet-friendly functionality, adds some things in desktop mode (I really like Task Manager for instance) but also took away a few things people liked as well.
The big question for me is what happens next. For some people who don't use computers as an end in itself, I think they'll be happy with tablets for their personal device, and maybe Metro/Modern-style apps are the way to go for those people.
But for people at work (and perhaps the students trying to work on a laptop); basically people who spend a few hours a day in front of a computer, something like Desktop will still be essential.
The big thing which means Metro/Modern will never work in a business environment without a substantial change is the lack of multiple windows. I'm forever comparing rows of values between emails and spreadsheets, or spreadsheets and databases, or databases and websites, or websites and a report from bespoke software; sometime comparing 3 windows from different applications at once, and this often needs to be windows "above-and-below" rather than "side-by-side". And the thing is I'm not even in a hugely technical role; there must be hundreds of millions of people who need to do the same, and that's before you get to the people with very technical or specialist roles who need multiple/ huge screens with 15 windows all visible at once.
Apologies to Ray8 for taking this quote out of context:
The cynic in me suggests that if, hypothetically speaking, you had an operating system with an Apps Store which didn't have many decent apps in it, then the above is exactly the sort of thing you might say to encourage developers to pull their fingers out and start writing some apps.
But for me, there are just way too many people who need functionality in multiple windows for a desktop-less version of Windows to be feasible as a corporate option. Likewise for all those students who need computers to write essays or whatever. (It's much more tedious to copy and paste from Wikipedia without multiple Windows )
Maybe Microsoft will branch off a business edition again, but that seems to be the opposite direction of travel to the smaller number of editions in Windows 8 compared to the number of editions for Windows 7.
So I hope that what Microsoft will do is to tidy up some of the Windows 8 oddities in a Service Pack, but keep the Desktop mode as a fixed part of the operating system (or make Modern/Metro *much* better) going forward. But if they don't, Windows 8 will still be good enough for me for a few years to come.