If I go to settings, or open the start menu, I have latencies measured in seconds, even though I have a fast gaming laptop.
As a comparision on my iPad most of the settings windows have about 0.2s rendering latency (some shorter, some longer), but in reality I don't see any reason why it shouldn't be the part of the continuous testing of any operating system.
Another important example is that I find it harder to find installed programs in Windows 10 than what it was in Windows 7, as Windows 7 grouped shortcuts installed by programs into folders, now I just see a big mess of shortcuts where I have to remember the name of the shortcut to be able to run it.