Same issue
The headphone remote/control works on a another iphone but not on mine.
Music does work , its only the controls on the headphones that don't work
Phone - Iphone 4
Tried restarting the phone, syncing the phone, resetting it from withing the phone, holding the buttons & then through itunes .. No use...
Issue happens across any pair of headphones including Apple's
Same happens in music app and 3rd party apps like spotify , tunein radio .
Can't use the buttons on the headphones to pick or answer call's as well .
I drive 4 - 6 hours a day and can't change songs on the go. Looks like this update screwed my phone .
The iphone 4s in my family is still on ios 6 and I don't plan on updating it . Tha's been my general advise to everyone I see and talk with a iphone , as this looks like a update related issue.