Having used Windows 10 daily for a while now on my main rig (my laptop's still on 7 since I use it for university), I have come to the conclusion that it's ... acceptable. No more, no less. I dislike the new start menu design (thank you classic shell for supporting Windows 10!), and it still has a few weird issues (see below), but on the whole its OK.
Would I install it as an upgrade to Windows 8? Maybe, my experience of both is equally 'meh'
Would I install it as an upgrade to Windows 7? Nope, 7 just works too well with all my hardware and software
Would I downgrade a Win10 PC to Win7? Probably not. As I say, it's not bad, it just doesn't give me any real advantages or incentive to upgrade, whilst still having issues.
Speaking of issues, my 2 main ones are as follows:
It's ridiculously inconsistent. To get some of my games to work, I've had to install and uninstall them numerous times in compatibility mode, but repeat the same steps enough times and it will just magically work... Well, when it doesn't BSoD, anyway... (also, for one of my games, there is a utility to preview meshes for content creators that WILL NOT render them properly in Windows 10 - random sections will appear transparent, and the inside is visible from the outside, yet they work fine in game, and the previewer works flawlessly in Win 7)
Second issue, WHERE THE HECK IS MY NOVEMBER UPDATE??? Yep, my copy of Windows 10 (pro x64) is still stuck on build 10240, because it never finds the november update using Windows Update. Other updates come through fine, but not that one. And my testbed laptop, which was clean installed using the same installation media, downloaded and installed it fine. Go figure...