1. What does it do? It changes to he color of your screen to represent the setting of the sun.

2. Why? Research has shown that being blasted with florescent light during the night time hours disrupts your sleep because its similar to daylight. So by tinting the screen you can be prepared for sleep.

3. Does it really work? Aside from the research, many of us have found it helps us fall asleep better when it comes time to head to bed.

4. What about late night design work. It can always be turned off. I have found it rare that I need to because on most of my designs the color pallet is decided at the start and I take from those colors. Again it can be paused at any time.

5. Cost? Free.

6. Whats in the update? You can now fine tune the transition at sunset, setting the middle part. New UI to make it easier. New "modes for watching a movie. Also new ways to snooze it.

So.... what changed?

I've been using flux for several years and it's easy to disable temporarily. Also, as a mobile designer, I'm mirroring everything to my devices to confirm colors so it's not that big a of a deal.