Apple didn't implement Night Shift as well as f.lux. In the evening, I like to have f.lux on and then when I'm ready to go to bed, I make my screen inverse with white text on black, to read a book. With f.lux, the screen properly turns black, but still has an amber filter. Night Shift, on the other hand, turns bright blue when I invert colors. It's unworkable for me.