I just set mine to Quito, Ecuador (anywhere on the equator will do). That keeps things relatively consistent throughout the year, instead of following sunset/sunrise times which have no bearing on my sleep/wake schedule.

Using location is more accurate as depending on how far away from the equator you are light levels can change drastically.

This covers some of the details around it: http://www.ccfg.org.uk/conferences/downloads/P_Burgess.pdf

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.

I agree. I live in Iceland and during the summer months it does nothing.

Many people aren't attuning it to outdoor light levels.