It's not a failed experiment.
'Success' does not need to mean, "Everyone universally enjoys this XXXX".
I'm a Windows Phone user as well as a Windows 8 user. I like both of them. I like that they've combined them. It works very well for me.
The interface needs to be refined in order to appeal to more people, but that does not mean it is a failure. It just means that Windows 8 was the first iteration of something that could/should/can be very, very good.
Taking the first steps toward a goal is not failure- it's building a foundation.
I own a Windows Phone as well. Right now, a Lumia 929 - the one from Verizon. It's great, as was the 520 when I had that.
Windows 8 on my Dell laptop, OTOH, was a pain. While typing, when the cursor would get near the right end of the screen, the charms bar would prop up, and there was no turning that off - even if I went into the desktop. Also, once I hit Start, I'd see the icons, but to discover all the installed apps that weren't showing up in the 'home' screen, I had to go south - something I accidentally discovered. I did try tweaking that thing, installing Classic Shell and so on, but the whole experience was really annoying. Finally, once I figured out how to install PC-BSD on it, I did it, wiping out Windows 8 from the whole thing altogether. After a few initial hiccups, PC-BSD now purrs like a kitten.
Another beef I had with that system - the native apps were something you now got from the app store, as opposed to the good old downloading it from a web site or inserting a DVD. This just felt too retarded. The other issue I had - if you have a Metro screen, why not have the possibility of multiple virtual desktops, particularly since the apps now insist on going fullscreen? That just didn't make sense - even in Classic shell, I'd be running, say IE, but if I went into Metro and invoked IE, it would go back there.
My point - the same interface on a touchless laptop and a phone and a tablet never made sense. On a phone, Windows 8 is just perfect, and the only thing lacking are some apps that I could use there, like ADP and Vonage. I don't mind games missing - I use that phone only for work. On a tablet too, Windows 8 is fine. On a touch laptop, it's at least usable, if less than ideal. If I have a 16" screen in front of me, the last thing I wanna do is touch it: even for my phone & tablet, I've put screen guards. But for touchless laptops, it absolutely sucks!
I am glad that Microsoft is finally bringing back the Windows 7 interface, at least in laptop mode. Windows 10 should ideally not take much time - they should just take Windows 8.0 (not 8.1), combine it with Windows 7 UI and give USERS the option of which interface they want when they start. Make the Windows 7 the default on laptops if users know no better, and make Windows 8 the default on tablets. And it's okay to have cute features like switching from one to the other, but allow people to turn that off if they like only one interface for everything.
Whichever it is