I have been very satisfied with Win10. only thing that was an inconvenience I had to do was disable the tracking/logging. Other than that I just don't mess with much and let windows handle itself (except active update hours - configured those for something that works for me and have been satisfied so far).
Honestly 10 is probably my favorite windows to date, and I've spent a lot of time using 2000, XP, and 7.
Oh, thanks, I forgot. Disable telemetry with O&O ShutUp10
Really, if you're on 7, at least get the upgrade on a cloned partition or drive or something. Win 10 is much faster (uses newer tech such as memory compression, which is much faster than using uncompressed memory pages, etc). That way you at least have the option to use 10 later.
EDIT: Oh, and look, the cleanest way to do this is a clean install, either replacing, or dual-booting with your current OS, after you complete the upgrade. Once you've finished the upgrade and gone online, your hardware is licenced for Windows 10 and you can clean install Win 10 straight from a flash drive onto a wiped or new drive, and it will auto-activate once it's online.
As has been mentioned, you can use a valid Win 7 / 8 / 8.1 key during a clean install to do the same thing, and you could get the key using Magical Jellybean Keyfinder
, however some AV software think it's a virus (it isn't, it can just *shock* read your product keys