I upgraded to iOS 9.3 yesterday. I had been waiting excitedly for Night Shift to be released. I set it to turn on at 12:00am and off at 11:59pm. Everything white turned yellow. My impression after one day of use: I love it.
I’ve been using f.lux on my Windows PC (on at the max all day) and on my MacBook Pro (on automatic control based on time of day) for a few weeks and I really find it pleasing.
4 April 2016: Still running Night Shift (on max — whites very yellow) all day, every day. I still love it. It’s a little odd when taking photos or video as I don’t know how the color will be in them.
17 June 2016: I still leave my iPhone 6 and iPad Pro set to max Night Shift 24/7.