I just upgraded a month ago. I'm still deciding how I feel about it.
Pros: the display is more traditional and less app-like. The screens seem more under control. I can easily find the shut down/restart button, for example, when I need it. I don't have to swipe in from the side, which I had found irritating. Accessing different programs seems more like the process I had been familiar with when I had Windows 7 and before. I didn't like the photo app in Windows 8. I haven't done much work with photos in Windows 10, but so far it seems more intuitive and accessible.
Cons: I've had so much trouble figuring out "Edge" (the new Internet Explorer), that I'm just using Google Chrome as my browser. There's also an annoying "assistant" called Cortana that is supposed to help you organize everything, but I don't feel like taking the time to learn. I just turned it off.
The main glitch I ran into was in how my mouse interacts with Windows 10. Suddenly I had to right click instead of left click, and couldn't scroll properly. I had similar problems with the laptop touchpad. However, I went into settings and changed the wacky defaults, and now this clicking/scrolling issue seems to be under control.
So, I guess I'm glad I upgraded since it seemed inevitable anyway that I would need to do it. I figured if I went back to Windows 7, I would eventually have compatibility issues with other programs. But I had the luxury of upgrading the day after my last teacher workday for the summer, so I knew I'd have a couple of months of less stressful time to tackle whatever went wrong.
I will be interested to hear what others have to say on this thread, as I'm still in the early stages of this myself.
Corey