For now, I have 2 machines running Windows:
My laptop - Windows 7 Home Premium SP1 64-Bit
My PC (mainly used now) - Windows 10 Home 64-Bit
I used to upgrade to Windows 10 on my laptop, which was the worst decision I made (besides buying it, since ASUS does not support Linux with drivers ect.).
But Windows 10 being pre-installed on my PC is pretty fine, since it is installed on a SSD - fast, decently looking, and stable.
Concluded (imo) Preinstalled > upgraded
Sure some things are better in Windows 7 (explorer, start menu), but I found my way through Win10, though, because of some stupid DRM, many games I own are not playable anymore (thanks SecuRom!). But for this, I have my laptop

What I loved about installing Windows 10 on both machines was the option to "use the recommended settings" - to send all data homewards to MS, and to use Cortana, which I find is a nice gimmick, but nothing more. My friends actively use Cortana, and probably use more of the possibilities Windows 10 provides - but as for me, I just need a working OS. Ticking off all location things and whatnot, I do not care anymore about the spying things.
Nowadays we keep using many things sending private data to the app's devs, we've become a glass society, where no data is safe anymore at any point, though using this and that encrypted services.