One thing about Windows 10 (and I guess this was true of Windows 8 too), is rather than being an operating system you add things to, there's shit you have to remove. Well, you don't have to. But if you wish to retain control over what gets communicated from your PC, then there's a lot to be suspicious of. For starters, every version of Windows 10 except Enterprise will send information about your computer and your computer use back to Microsoft *and their partners*.
Furthermore, Microsoft provides a lot of apparently simple apps as default and who the hell knows what they do once they're finished displaying your pictures, movies, documents, etc. How closely are they tied to this "telemetry" Microsoft collects, and why are they so simple to use you can't change any settings? Replacing them with genuinely useful programs is easy(ish). Removing them is difficult. You have to screw around with Powershell.
Ladies and gentlemen, this is not new. Google and Apple do this too. Further than that though, large scale exploitation of unowned resources is not in the least new. Oil, coal, gas, fisheries, forests, the goddamned air you used to breath... and now "telemetry". As with all unowned resources, a generation too late we're going to discover that, well shit, all that crap the companies collected and exploited for profit, we did own it, no matter how often they said it was just stuff they found.
I think probably Windows 10 can be made mostly safe to use. I'm annoyed at all the crap I have to learn first. What set me off this time was discovering that Microsoft has finally done it, they've included directories on your computer that you can't access without complicated shenanigans akin to the gaining of "root access" in Android. (\Program Files\WindowsApps) The difference with Android is huge numbers of people do it. In Windows, it's a throw your hands in the air kind of deal and you have to ask is it all worth it.
And it is all worth it? It might not be. I haven't worked out what benefits Windows 10 offers yet.