Rene Ritchie, iMore:
iOS 7 was more than just a redesign: It was a reimagining of what mobile interfaces should look and act like. Part of that involved a lot of flat, white space. A lot, a lot. It made the iPhone and iPad look bold and bight, which is fine for everyday use, but when it comes to low-light situations — like the home theater or the bedroom — it can be a little too bold and bright. If you're not careful, it can get you yelled at and hit with a pillow. It's enough to make me wish for a dark theme in iOS 9
Like Rene, I would love it if Apple introduced something like this in iOS 9. I run any app that has a dark mode in it all the time and I'd likely do the same with a system-wide solution for iOS. Not only does it make apps look better but I find it helps me focus on text much better as well.