I've used f.lux for years and I really like it, as I have noticed my sleep patterns have improved during that time.<p>However, I do think that the transition is sometimes really too quick. I can be working away, deep in 'flow' and I will alarmingly perceive the screen going darker/changing a couple of times over the evening. It almost feel like I am passing out or getting a precursor to a migraine sometimes, with the change, which is quite jarring.<p>The other thing is the constant annoying notifications of "You are going to be awake in 'x' hours". Well, actually, no - If I am up and coding until 2am, then chances of me being awake at 6am when you expect me to is just not on.<p>I also wish they would have an 'emergency awake' function, so that when I jump on to the keyboard to fix a server outage at 5am after many hours away sleeping, that it would immediately go to full brightness there and then, rather than wait until 0630 as per normal. If I am active at that time after a long break, I am NOT going back to sleep and I have to have full illumination of all those red signals on my server dashboard! :)