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My general rule of thumb is to stay on the iOS that the phone came with, for the best speed. I'll update to iOS 8 if they speed it up to almost iOS 7.1.2 speed and when some bugs are fixed.

This ^

Great advice. I only update months down the line once I am absolutely positive that the iOS update doesn't affect speed or battery life. I am perfectly fine with keeping whatever iPhone on the iOS version it came with for as many years as I am using it.
 
Smooth and fast, typing especially. Same battery life as 7.1.2 for me, from 7am - 11pm between 10 and 20% left. Have 5 push email accounts running plus I make/receive a few hours of calls a day. Also running Bria VoIP app for 6 hours or so (battery at 10% at 11pm).

Screen brightness on auto, slider at 30% ish, location turned off on set date/time, weather etc.

Upgraded over 7.1.2 on all devices, did a settings only reset on the 5S as it was initially choppy. After reset all good tho.
 
never liked his "reviews". From those 8 minutes maybe 4 minutes are usefull and still he looks like amateur reviewer after tons of "reviews" ;)

he is actually ok to listen to out of not many reviews on iOS 8 i tried to find on YT.
 
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