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I have had the opposite experience with my iPhone 5. After installing iOS 7, my battery gauge accuracy and longevity has improved. :)

Lucky! Mine was abysmal before iOS7; now it's worse. took it off the charger this morning, did some light browsing, Candy Crush, FB, email, the usual. One hour, 1 minute usage = 50% drain. I can't friggin' WAIT til my new phone gets here. Even if the battery life blows, it's GOT to be better than this crap.
 
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