f.lux was available for OSX until Apple forced its removal. In an ironic twist of events however, Apple is including this very same feature in iOS 9.3, called Night Shift. That is not the focus of this article however, so lets move onto the desktop version.
So lets see the difference. This is my monitor without f.lux running...
Enabling f.lux noticeably reduces the amount of blue and makes the whole picture take on a red tinge.
At first this transition doesn't feel very natural and the colours do look very off, but after a few minutes your eyes adjust and you don't notice it as much.
Here's what the transition looks like...
Ok so did I notice any difference in sleep patterns? Well honestly I can't say that I've noticed a huge difference. However the colour temperature change works really well as a reminder that it's evening and maybe you should get off the computer and relax. In addition, the redder colours do tend to make my eyes feel heavier. I guess that's the intended effect, but it is subtle.
Will I continue to use f.lux? Yes and I would recommend it to others just don't expect a complete change if you were having difficultly sleeping after working away on the computer for the whole night!