Nope Windows 10 isn't ready yet until they fix the activation servers.
It seems when you do the upgrade it uses a default CD-Key and doesn't ask you for one. But in settings you can change the key if you wanted to change it. It activates by your hardware profile and when you download the ISO and do a fresh install you don't enter a CD-Key and it activate by your hardware profile.
But right now the W10 Activation process is borked. Hardly anyone can activate their copy.
Well GNU/Linux for me either Mint or Lubuntu or maybe SteamOS. Run Windows 7 Pro in a virtual machine for the Microsoft Windows apps.
Windows 10 was fun until it wouldn't activate. Gotta love that DRM and online activation that doesn't always work properly.