I use F.lux and like it, but there's one thing that Night Shift has that I can't seem to replicate with F.lux - the ability to toggle it on/off whenever without having to stick to a schedule. From what I can tell, F.lux is limited to coming on at sunset or a predefined time, but can't easily be toggled on at a different time without going digging in its preferences, unlike Night Shift, which can be turned on and off with the tap of a button in control center whenever you want. Unless I'm missing something? If so, I'd love to know!
However, if this is really how F.lux works, I really hope Night Shift comes to the Mac this summer. I work odd hours and don't necessarily want my computer's color temperature to change at sunset all the time, or even at the same time every day for that matter.