Same. It's funny that the primary reason I haven't upgraded to iOS 7 is because I like my screen red at night. F.lux is the one tweak that I can't live without, and probably would consider a switch to Android if I couldn't make it happen on iOS.

Apple should just implement f.lux-like behaviour in OS X and iOS, maybe with an API to allow it to be disabled temporarily (for Photoshop, etc.)