I think the gist isn't to match the outside so much as to set a pattern of turning on F.lux at the same time every day, to settle into a night-time routine.
I know the reasoning, I guess I'd just prefer to set it manually based on when I'm actually using my machine. As in, near the end of my usage at night I want it to be very orange no matter what the time is.
This covers some of the details around it: http://www.ccfg.org.uk/conferences/downloads/P_Burgess.pdf