Well in my case the november upgrade (Th2) made my notebook's switchable graphics have problems with older games. Before that I had nothing but praise for Windows 10. It is faster, more responsive and a better OS than Windows 8
If your system is running great with windows 8.1, then there is no need to upgrade to windows 10. It will be a long while before windows 10 becomes completely stable and mature with a majority of the systems out there.
@acme: If a notification turn out to be an error or something wrong the license key, hence its considered to be counterfeit; but as @Umbra said its strictly to know where do you bought that laptop.
My suggestion would be to dual boot Win 8.1 and Windows 10. Test out Windows 10, see how well it runs. If you like Win10 you can stop dual booting and upgrade Win8
Also, in case you want to upgrade the hardware of your PC, you can still be eligible for your license.
According to Gabriel Aul, you can contact Microsoft Customer Support after the hardware change and you can regain eligibility for your Windows 10 license.
So don't worry about Windows 10 not liking hardware upgrades, you can pretty easily take care of any nags from Windows 10 after you upgrade your hardware.