It's balls.
turn off mobile data + 3G/LTE when using wifi
Turn off wifi when using 3G/LTE
Ios 7 uses both wifi and cellular radios in tandem to improve response times for iMessage, Siri, push and cloud docs.
You shouldn't have to shave all the other features back on an $1000 phone!
Just remember to turn off the radio set you're not using.
I get *close* to ios 6 times when I do that.. With push/cloud/find my/iMessage on..
Standby seems great (unless wifi and cellular are both on, then it sucks the moment my screen lights up)
Hope they improve its management in the next update or I'm gone. Carrying a charger around is bulls**t