I have never had problems with sleep because of blue light from my monitors, nor can I say wether or not it's "dangerous," but in my experience it definitely does cause temporary eye strain. In a dark room, using a blue light filter makes a world's difference when it comes to how "dry" my eyes feel, how much I need to squint, and the eventually developing head ache. Granted my methods for testing this aren't very scientific, but it does help me, even if it doesn't make a difference in the long run.