It doesn't appear to have the ability to adjust effects according to the time of day. That makes it unacceptable for me since f.lux and Iris both do it.
It also doesn't appear to have slow transitions, meaning that effects are applied immediately when you enable it.
I don't want to sit down at my Mac in the evening and have to manually enable it, then have the screen suddenly dim.
Even worse would be the sudden change from dark to light in the morning when I manually disable it.