Reset all
My iPhone 4S had major slowing of the wifi after the IOS6 update and I was reluctant to try most of the options presented as a "fix". In the end I did try them in increasing order of "pain in the arseness". The only one that worked was "Reset All Settings", which was a major annoyance, having to re-enter wifi passwords, lock codes, background pictures, ring tones etc. but at least I have decent wifi again.
Biting the hand that feeds IT
