iPhone 5 shuts down at 25% on iOS 7.0.4
I called Apple about this and they said 2 things:


the numbers provided are approximate 
certain apps in background can be battery hogs. She specifically said that the camera app native to iOS7 continues full battery use in background and they were aware of this. She suggested being careful NOT to keep camera in background (i.e. double tap iOS button and slide camera up to remove from background active list)


This must have been the problem for me because battery life immediately improved. It still shuts down soon after going below 20% but it had been at 25% when I called.