I was running 8.1 just fine, then one night I took a nap, woke up, and it auto updated. Then this update happened the same way, when I was asleep.
https://www.reddit.com/r/Windows10/ an entire reddit section, nothing but various complaints about the update.
My personal PC kept asking me to update again and again to the point I had to ctrl+alt+del and shut the update down, clicking NO, NO, NO, do not remind me later, do not update, etc.. It was a chore for a while to say the least.
There was a guy I knew who did the update at work and he was basically off his PC for two weeks. the problem being old hardware apparently can not handle windows 10, whereas PC's which come with it pre-installed work fine.
It's all a sham, I loved 2000 and XP Pro was such a good system. W7 I was 50/50 on but I am used to W8.
MS' "Free update" for W10 was also bogus, because users still have to pay licencing fees every subsequent year of use. I'm glad that I've kept a few older versions of windows on disc in case I ever just want a PC which runs "off the grid".