My own opinion: 10 is based on nt6 like vista and 7. It eventually became a stable platform. I'm not worried about the 10 core os being unstable, really am just worrying about the new versions of programs that come with it that might be. 10 is more or less windows 8 done right. Sort of like how 7 is vista done right.
I actually did like vista a lot sp1 on up. While other people lamented it, my using of linux really made me like it a lot. Plus i enjoyed the actual program upgrades from the previous versions of **** found in xp. Aside from needing more horse power, that users didn't find it familiar (this point i really find moot, i didn't have a problem with the start menu not saying start), and that vista from day one had problems from stability and drivers from manufacturers; when sp1 came out, it was a hell of a lot better than xp (uac clone of gksu for the win!!!!; if you don't understand not running as administrator 24/7, then you don't understand why uac exists, and why this was one hell of a thing needed for so long).
I'm quite fine with nt6 stability. Just worried about the new programs that are required to run with it is all. This is why i don't mind the upgrade to windows 10. Control panel got ****ed with, oh well, i'll learn and live with it if possible, but most likely possible. The mini start screen start menu; fine, classic shell for the win.
We're not going from one version of nt to a completely other here like with xp to vista. I don't fathom many problems aside from ironing a few bugs that comes with a new release. And we probably shouldn't see many, or at least not many that will concern or affect me. After all, we're essentially dealing with a better release of windows 8; that i will install classic shell on (omg!!!, i really don't care for web content popping up in place for what i have locally installed when using the start screen, that greatly impedes and confuses the user, and the tech support that i perform at my job; yes, upon finding a windows 8 computer i am working on, i do ask if they would like a normal start menu, and that the change will take about a minute, most say yes to classic shell).
This is why for the money (unless you run a highly detailed setup, which i will call genericly win7/vista legacy(for the hell of it), don't upgrade, or don't upgrade because you don't want too).
Not to say that i don't disagree with the direction to a point where microsoft wants to take their os. I have always strongly believed for a long time that you put what the user wants to do first ahead of what the product wants, and even wants you to do (i do get into the nitty gritty with that; i always turn off aero, hardware peformance goes to the user), a start menu that suggests web links over a program you have locally installed is counterintuitive and confusing. Classic shell fix.
Whenever i load out a windows 8 computer, classic shell is installed by default. Yup, i know my users.
EDIT: My only rant with vista, 7, and 8 is that explorer.exe sure does crash a hell of a lot more often compared to xp.