My nightmare was over an older update of Windows 7. KB3022345 caused a corruption of two .json files that couldn't be fixed in the system file checker - which resulted in the "blinking desktop" that nearly caused me to lose all my hair this weekend.
Fortunately, I got the files fixed, deleted the updates that caused the problem, backed up my old Win7 environment as a "clone" onto my external HD, and dove head-first into the Win10 upgrade experience.
I think I let out a yell of joy loud enough to be heard in Redmond when my desktop showed up.
Lot of little annoyances and naggings - but most of them are because I'm still so old skool: I've gotten used to keyboard shortcuts, so imagine my surprise that ALT+F+N+F no longer created a new folder, but CTRL+SHIFT+N did.
I'm also not really liking the white toolbar/address bars in Win10, but I'm figuring some enterprising person is going to figure out how to alter those pretty soon.
Basically, just finding where things are, playing a bit with the Start bar, getting myself comfy with the new interface. Nothing completely new, of course; I've gone through so many OS'es in my life, I think even Mr. Hodges would be impressed.
...well, maybe.