My months old ACER runs Win8.1. I hate the amount of work involved in navigating so I clicked the reserve Win10 icon, but I waited to see the public reviews before allowing the upgrade. I was naive.
My kids call me overly paranoid, but I never allow auto-update and most things they take for granted aren't running on my machine. Because of my paranoia, I was able to stop the Win10 upgrade. Apparently since I'd 'reserved my copy', Microsoft felt they had the right to force it on me. There is no option given to delay or disable the upgrade processes. I'd come to update Win8.1, not jump to Win10 so I bailed out.
I decided to clean install Win8.1 (yes, I'd made the backup image right after I bough the machine, thank gawd) but I wanted to save some time by retrieving the list of KB updates I'd hidden and in doing so, I stumbled into the valid updates I needed for Win8.1. I haven't done the reinstall yet, but I'll be reviewing every KB update for any sign of Win10 upgrade support and those won't touch my machine again.
If Win7 included support for the tablet's touchscreen functions, I'd be installing Win7.