Same story here.
My iPhone 4 was working flawlessly and battery charge was lasting up to 2 days of normal use, until I upgraded to iOS 7.0.2. After being forced to update the battery drains from 100% to 0% in 6 hours in standby and one 15' phone call would kill about 40% of battery charge!!!
The phone is unusable as it is now as I need to keep it constantly plugged to charge to be able to have few hours of autonomy in normal use!
The problem is 100% software-dependent and iOS7-dependent.
I change the battery with no better results, and, again, no problems whatsoever before iOS update!
Basically Apple policy of forcing me to update my device against my will and installing a broken operative system screwed a perfectly fine device!!
Apple store solutions did not work. They restore the system at factory default with no improvement!!
As Apple does not admit this problem, I doubt they will work on a fix with the next upgrade of iOS7.
My iPhone is screwed ....and Apple lost forever a customer. I reluctantly will buy a Samsung now.