I voted on this buy moving from ios 7 to Android
For me it was international symbols which meant nothing to me ....
If you accidentally swipe from the bottom up a screen comes up with a load of comprehensible ikons. I had accidentally touched the 'do not disturb ikon
That caused all incoming calls to go to voicemail.. After several weeks I lost patience with it and put my sim card in a phone that would ring when someone phoned me !
On trying to restore a previous backup using iTunes the updated latest version of Itunes no long recognised I'd just plugged by phone into the computer. that followed upgrading my ios to 7 which blew my contact list away...
So if you have a iphone 4 do not upgrade the ios to 7 ! IMHO unless you value the hugely improved compass ! *LOL*