Since I've upgraded to iOS 7 it says I've used 458MB.
My battery doesn't last long enough to use the phone anymore for anything other than txting or emergencies. The music app isn't reliable enough to use anymore. Constantly needs to be closed and reopened or it panics and reboots the phone.
Before iOS 7 I used roughly 2.2GB a month. I refuse to carry a charging cable with me. Never needed one before. iOS 7 pretty much turned my phone into a Windows device. I have to reboot in order to get iMessages to work and that only works half the time. Screw it, I've posted enough about this garbage. Apple needs to fix it soon to save face. Even CNN is trying to give out advice on saving battery life with iOS 7 and has run multiple stories on it since release.
My advice, if you're still lucky to have iOS 6 keep it. Wait until iOS 7 is fixed. Control Center is nice, but so not worth the hassle