Windows 8 was doomed simply because it was a radical shift from what people had been used to going back to Win95. Sure, In between Win95 and W2k there was some face lift stuff done to the UI to tweak and polish it, but basic functionality remained the same - Click Start, find your program, click on it, go to work. If you needed to fiddle with settings, you click on start and click on Control Panel
Trying to cram a touch screen style interface down the throats of point and click users..... of course that was going to end badly.
I personally don't upgrade my windows versions quickly and easily. I stuck with Win95 until Win98 SE, then upgraded to W2k after SP2, XP after SP2, skipped Vista entirely, and upgraded to Win7 when games I wanted to forced me to.
Looks like I'll be skipping Win8 entirely too. I will certainly take a look at Win10 when it becomes available, and I might consider upgrading to it if the UI isn't too much of a pain in the ass.
Hopefully Microsoft has learned that there's no money in the desktop OS market anymore, not with other vendors providing cheap or free installs and updates.
If Microsoft makes Win10 something that's not a pain in the ass to use, for a relatively cheap price, and capable of joining an AD domain, I'll probably use it on a more permanent basis, but probably not for the first couple years of it's life unless there's a *really* compelling reason to do so