I will not upgrade to Win 10 for the PC I'm writing this now ( Win 7). Some of my old games not even working on Win 8.
I also will not upgrade to Win 10 for my laptop (Win 8.1). Someone I know already did it and a lot of crucial app for work no longer works (they said Win 10 automatically removes the app. !!? )
But if I buy a new PC in the future, Win 10 is obvious choice.