One month ago I bought gaming PC with Windows 10 for my son and I helped him to install some programs and games. After 3 years of exclusive usage of OS X, my first impression of modern Windows 10 was "hm, it looks great even on 4K monitor (UI scaled well), takes few seconds to load and works fine - maybe I should try it again". Only annoying thing I found is extreme level of espionage in OS and fact that sometimes Windows will install updates and reboot even if I don't want it.