That iOS 7 was designed for the 5S. Have you not paid attention to the videos apple advertised? Perhaps maybe these stuttering animations and hiccups are because the OS was designed for a 64bit processor on the 5S? Ive noticed the parallax effect is jittery. I also noticed the 5S has the m7 coprocessor built specifically for things like that. Coincidence? Doubt it. Wait until you use it on the 5S and we'll see.