Same issue with iPhone 5. Since latest uptade internet seems to be really sloow and not as good signal strenght as it use to be before... Before, evenen when I had no 3G i could just go through settingse switch3G off then on and it was improoving signal strenght. Now even that is not working. Not as much issue with wi-fi but again, it's not as good as it used to be.
waiting for the problem to solved ASAP