Based on the fact that actually trying to use it is like having a 300 pound gorilla with steel toed boots on kick you in the face repeatedly for 72 hours.
Anytime you open a new screen in Windows 10, like your printer devices for example, the OS goes into this ten minute search mode which locks up your system and prevents you from doing anything else until it has finished counting it's fingers and toes.
Then when you are looking for control panel settings you have to remember now if that setting exists in the old style control panel, or has it been moved to the new Playdough control panel.
Then there is Microsoft's betting on the fact that we would all be using touch screens by now. Newsflash, we're not. And you will struggle to even find decent touch screens on sale for less than a bazillian dollars. So why not offer a desktop mode option that locks down all that childish flashy playdough crap if you don't need it or want it.
And finally there is of course the above update and restart problem. This thing does more updates than my Portuguese neighbour giving the local neighbourhood gossip over the fence to her friends.
I think this things has downloaded about twenty full copies of Windows 10 since I installed it six months ago. What the ever living hell? Just pick one version and stick with it. Or offer me critical updates only.