When comparing NoSleep vs F.lux, the Slant community recommends F.lux for most people. In the question“What are the best Mac OSX apps for someone that's new to Apple?” F.lux is ranked 5th while NoSleep is ranked 26th. The most important reason people chose F.lux is:
Helps provide better sleep for more energy during the day.
Ranked in these QuestionsQuestion Ranking
Pros
Pro Lets you close the lid of a laptop
The laptop will not sleep even if you close the lid, but the display will sleep. If your display cannot sleep, simply lower the brightness until it goes dark & turns off.
Pro Can help sleep better
Helps provide better sleep for more energy during the day.
Pro Eases eye strain
Decreases color temperature at night, changing the normally fluorescent blue of an LCD monitor to a soft orange. Much easier on the eyes, especially in a low-light environment.
Pro Subtle transition
The transition from daytime to nighttime color modes takes an hour by default and will detect your current timezone, meaning that it will happen in the background at sunset, often without you noticing.
Cons
Con Discontinued development
Latest release was November 15th, 2014.
Con Takes a while to get used to
After installing F.lux, the screen will look a lot more yellow. This takes about a week to fully get used to. You can ease into it by setting the color temps higher than the recommended defaults.