I have kept the factory sights on all 7 of the Glocks I owned. Got used to them over the years and now prefer them over three dot. I did appreciate the adjustable sighs on my Glock 24.
I don't care for the stock sights.. I seem to see the three dot system that is on the night sights much better. I also mod some pistols like the pic below with a "straight 8" type config with luminous paint. I reverse the rear sight in the dovetail, spot it with a small drill and put a drop of the luminous paint in the dimple.. Just my personal preference, and it's CHEAP to do....