Ever since my friend referred me to this app. I cannot live without it. I installed it on my mac, iPhone 4 and if I jailbreak my new iPad it will be installed on there. f.lux adds a warm tint to your display making it relaxing to look at. So when it comes to staying up late in bed checking your twitter what not / etc. Your brain wouldn't stay awake as it would without having something like f.lux. If anything polarized sunglasses adds the same effect. : P