I must admit to being a bit hesitant to try f.lux when I first heard about it. The premise, that altering the colour temperature of your computer screen could improve your sleep, sounded like an April Fool's joke. In addition the homepage is full of testimonials from happy users which make the product sound like the latest pseudo-scientific nonsense so beloved in the debunking by Daniel Rutter. However, I am now a believer.
The software is free, for Windows, Mac and Linux, which in itself is a sign of quality. It runs in the background, and as day turns to night it adjust the brilliant white of your monitor down to a warm incandenscent-like orange glow. I didn't expect to like it, and on first use I didn't. However, over the next few days I became accustomed to the new colour. Now, when I experimentally turn f.lux off briefly I can't believe the harsh light that used to assail my eyes. I don't know if it improves my sleep, but it certainly makes my eyes happy.