I appear to be having better than average battery life with my iPhone 4S on iOS7 (AT&T), but my wife saw drastically reduced battery life. We reviewed her settings and she had a lot of apps with Notifications turned on that she knows were off previously, so we corrected those. We also changed her email settings from Push to Fetch (Push is a battery drain). We then did a hard reset. Her battery life seems to be back to normal. (EDIT: I take that back. She just told me the battery life is better than it was after the update, but still below normal).
Regarding the hard reset... I've found that sometimes after doing an update, battery life is diminished but a hard reset cures it. It seems that "something" is hung up in the background sucking down the battery and a hard reset (reboot) corrects it.
One other note... we did the equivalent of a "clean install" by restoring the firmware through iTunes, then restoring the backup. That seems to be the best way to go about upgrading for major releases. Someone I work with upgraded to iOS 7 via his iPhone's own updating mechanism and he had some weird error message (I forget what it was now) that required a restore to resolve. Prior to this restore, he had never connected his iPhone to his computer in the 2 years he's had his 4S.
Oh yes, as for performance, iOS 7 is buttery smooth on our 4S iPhones. It's an AWESOME update with a lot of long overdue features. This time last year, I was very unimpressed with the progress in iOS 6 and iOS 7 had to be good, or else. I think this really shows just how ineffective top management had become in working together until Scott Forstall was canned. This was a heck of an update to pull off in, what, 9 months since then? I see only GREAT things going forward with Tim Cook taking charge.