iOS 7 is absolutely destroying my 4S's battery life on.
I'm getting about 2 hours of use out of it before it's completely dead. Yesterday it died around noon from very little use. It seems to just eat resources while not in use. Maybe there's some backend GPS stuff going on that I'm not seeing or something.
Luckily, I can keep it plugged in and charging basically everywhere I am throughout the day, so it hasn't been too big of a deal. Just a bummer.