You know Apple have got a problem inventing new features, when the number one feature of the newest IOS update is just a feature that alters the colour of the screen slightly, for nightime viewing. It is a feature Android has had for over a year, so it is just playing catchup anyway. These products are now so mature, that it is now going to become a bit of a race to the bottom if they want to compete. I mean what other features can they really add, apart from improving battery life.
You've been able to download twilight which does the colour shift for android for years, I had f.lux running on my jailbroken 3gs iPhone back in 2011. I think the concept of having a different colour temperature for assisting the circadian rhythm has taken that long to become mainstream enough for Apple to adopt it as novel.