The thing is, if someone upgrades to Windows 10 and doesn't like it, they can roll back to Windows 7 or 8.1. Since I like it, I'm staying with Windows 10.
The point is if you install Win 10, you can roll back to your previous operating system. If at some point later you decide you do want Windows 10 it will install and be activated. If you have never tried it or activated your system, you will have to buy Win 10 if needed later. No matter what you choose, if you continue to use MS Windows you will eventually have to use Windows 10. It's pretty simple if you hold on to WIN 7 it will continue to receive security updates, until 2020, but it is no longer a main stream supported operating system, meaning nothing new in the OS.
I do dislike not being able to turn anything off that I don't care for, but I would guess a third party option to turn it off will be available fairly quickly.
It's a love hate relationship. The bottom line is if you don't want it, don't worry about it, it's gone tonight and the GWX notice will soon be removed.