The problems with IOS 6 and WiFi are real. Many iDevices that never see a captive portal may not see the issue.
My iPad 2 (IOS 6) works great at home and not so good on any captive portal I have tried. Going to a hotel for weekend or McDonalds or work and I see bad issues with WiFi connectivty (I have to renew my lease everytime the iPad shuts down and always have a slow connection)
Does the router just need a firmware upgrade/downgrade or just resetting? I do not know, I can hardly ask McD's to let me tinker with their WiFi network.
How do I know it is IOS 6? Well my iPad worked fine before I upgraded. My son's iPad 1 (non upgradeable) works without an issue, my wife's iPhone 4s (she refuses to upgrade) works fine.
Draw your own conclusions, I have mine. The refusal by Apple to even acknowledge there is an issue is starting to irk me especially as there is no easy way back to ios 5. With the exception of my soon to be out of contract Blackberry we are an Apple family and I'm starting to have second thoughts about my next phone.
Also.... IOS 6 battery life seems suspect, not so sure it is a coincidence that my battery life has dropped significantly since "upgrading"