In a related but different issue, my iPhone 4S has not been able to connect to wifi since I upgraded to 8.0. 8.1 didn't fix it. It notified me of some patch today; I hope it works.

I tried a few different tricks I found by Googling, like "Reset Network Settings", but they didn't work. It's weird, after upgrading to 8.1, I had Wifi for a short period, then the next time I came back to my phone it was back to being completely gone. As in the Settings app won't even let me turn it on.

Pretty frustrating.