WIn10 Disbeliever (me).
I have them all, old Inspiron 570 with Win7, my gaming PC (4790K with mild overclock) with Win8.1 and a few old laptops, which got free Win10 upgrades in the past.
All my Windows looks like Win7, because I use ClassicShell. Win10 has nothing to offer new to me (and possibly to a lot of people) except DX12. And I really hate Win10 for forced updates, especially for laptops.
Remember Anniversary update, which caused so many problems with laptops? Therefore, I completely disabled forced updates on my laptops, I revert this process once in a while or forcing certain update when absolutely necessary.
Win8.1 is promised to be supported till 2024, that is enough for me.
Regarding slow systems, My older...