I've put Windows 10 on one of my laptops and it's fine, But on one it screwed the keyboard, half worked half didn't.
So I'm now running Windows 7, Windows 8.1 and Widows 10.
I'm very suspicious as It's free, Microsoft don't give anything away.
You can't switch off automatic updates, so if Microsoft wanted to follow Apple and only let you run programs purchased from them, they could quite easily.