If you are a Windows 7 or Windows 8.1 user, this is important news for you. From day after tomorrow, Windows 10 won't be a free upgrade any longer. So get cracking, upgrade to Windows 10.
If you are on Windows 8.1, you get back a familiar Start menu but retaining the best parts of Windows 8.1 There's Cortana, a new app model, better performance, security, etc. It's a no-brainer.
If you are on Windows 7, well, then you are generations behind. This is a huge upgrade in every way, yet is familiar unlike 8.
The best part about the Windows 10 free upgrade is you'll never have to pay for an upgrade again. It's going to be updated free till your device lasts. In fact, another free upgrade is coming to Windows 10 users on August 2nd.
So, even if you don't want to use Windows 10, it might be recommended to upgrade to it anyway, get that free license, then roll back to your current OS if you are unsatisfied. Then in the future, you can upgrade again to Windows 10 for free - despite the fact that the offer will be over then.
Finally, there are some cases where Windows 10 is not the, yes, but then if that's you, then you don't need me to tell you about it. For most people, it's a must upgrade.
What are you waiting for? Go get the free Windows 10 upgrade!