Also worth a look is redshift (in the repo's as gtk-redshift if you want a a graphical control) which is basically f.lux but works better on Linux (in my experience).

I don't know if all the stuff about blue colour curves and stuff is accurate but what I do like is that it reduces the "staring into a lamp" feeling you get when the sun goes down (and in the UK at this time of the year that is pretty early).