I have known about it for a long time, but only recently tried it out. Links to scientific research on light and sleep are provided on their site.
Nighttime Computer Use Made Easier On Your Eyes and Brain
I installed f.lux on my computers Friday night, and my eyes and brain immediately felt better. I did not feel eye strain go away, as some people describe, but felt more relaxed and tired (as I was! it was late and I was feeling like going to bed!). It was soothing.You can read comments about it, pro and con, on Macupdate, idownloadblog, PCWorld, and etny.