iOS7 on my 4S is pretty good for me... now. When I initially installed it was a hog. Here are some of the settings I've tweaked:
Settings > General > Background App Refresh : Turn off almost all (left Maps, Reminders and Weather)
Settings > Privacy > Location Services : Again, turn off pretty much all of them.
Settings > Privacy > Location Services > (all the way at the bottom) System Services : All off for me.
Settings > Privacy > (all the way at the bottom) Advertising : Limit Ad Tracking
I have mail set to push (using iCloud which gets all my gmail pushed to), and i left Apps to Automatically Update... I love this feature.
Battery is pretty solid, about the same as iOS6. If I charge it to 100% overnight, I'll drop a percentage or two MAX in 8-9 hours. Phone lasts all day with decent charge at night (20%-40%) depending on my daily usage. Those Location/Privacy settings were eating up my battery.
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Do you guys think Parallex affects iphone 5s battery?
Not sure about the effect on Battery, but on my iPad 3 the dynamic background was causing some lag so I had to stick with the static backgrounds. I suppose all the parallax movements could somehow use more processor thus more drain on battery. Wont hurt to try.