So far, I'm liking what I am seeing. Only a few little gripes and I might accumulate more but for now, not bad.
For starters I don't know if it's the new NVIDIA drivers or if Win10 is actually optimizing it better but GTA V runs like butter. I know it's still running on DX11 but before where I had to turn off a features I have just about anything I want turned on to Ultra fullscreened at 2560x1600. I'm leaning to something on the OS side because I didn't change my GPU (980ti) for the upgrade.
Can't say I miss the "metro" or whatever it was officially called in 8.1. At most I'd just hit the Win key and type what program I wanted, so now actually having a Start button back is odd to me. Maybe I'll look into organizing it with tiles to how I want but most likely not, we'll see. From what I've messed around with in there it is pretty slick though.
I usually prefer clean installs with my operating system but in this case, you can't really do that because of tied keys blah blah. I've done Windows "upgrades" in the past, like when I tried 7 to 8 and it told me it saved all my programs then slapped it's dick in my face and said lol nuh uh, a Windows 8.1 to 10 upgrade actually kept all my software and even the icons on my desktop. The future is here!
Microsoft Edge is the first time I've used a MS browser since 1995 when I was a dumb baby and didn't know any better. It has been surprisingly nice and seems to take less RAM than Chrome does (I don't think I like Chrome anymore anyway). Obviously missing extension features, etc. I've had to go back to blocking ads through my host file to keep using this. Did Firefox ever fix their shit? Oh well.
If you are still weary, maybe try it out first in a virtual desktop. But it's been a solid experience to this moment.