So Im a convinced f.lux user, have been for just over a year. I believe it does reduce eye strain and helps me sleep better. So I was waiting in anticipation for 10.12.4 and the integration of Night Shift in macOS. My main problem with f.lux were the problems when playing videos full screen and the issues that was causing. So I upgraded threw the switch and took Night Shift for a drive. I have to say Im a little disappointed. One of my favourite things about f.lux was how it adjusted based on time i.e. the sun sets and the later it gets the less blue light is displayed. Whilst Night Shift turns on automatically on sunset, it is set to one single colour temperature throughout the entire night, so it doesn't adjust like f.lux. I loved this feature as it made the transition from daylight to "night mode" feel seamless and you almost wouldn't notice it unless you turned f.lux off. So I'm unconvinced with Night Shift, and am not sure whether I will use it over f.lux.