Windows 10 is stable and is what Windows 8 should have been. Microsoft is pushing to get Windows 10 on every Windows machine possible, making the upgrade from Win10 and Win8 very cost-effective -- free!
Most 64bit Win7 machines will upgrade to Win10 without a problem. If you are upgrading from Win7 and your machine can accept another memory chip -- it's probably worth the investment when you move to Win10.
Plus, if you are upgrading from Win7 to Win10, you will find the transition relatively easy. Win10 defaults to a very familiar-looking desktop. The learning curve from Win7 is minimal. Most of the annoyances from Win8 are gone.
If you are upgrading from Win8, you'll wonder why you waited so long!
That's the good news. The bad news is that almost no computers that are still running WinXP have the capability of running Win10. Also, if your Win7 computer is a 32bit machine -- you're out of luck; Win10 will not run on a 32bit machine.