I've owned and driven a number of planes with eyebrows, B737CL, Westwinds, & Astras... They give a nice spot to put a tracker system in without chopping new holes in the pressure hull. Otherwise, keeping the sun shade in place is the main justification for what they do. Even in close form trail they don't get used.
I flew 737s with eyebrows out of Perth. They were very useful in visual circuits and circling. On a base turn to the otherside (i.e. flying left seat and turning right or vise versa) the threshold is nicely visible in the eyebrow window.