WIFI disabled - Greyed out since iOS 7 update on iphone 4s

You can just download the iOS 6.1.3 iOS, google it you can restore back to that verison.

Wi-Fi settings greyed out or dim

I tired resetting the network settings. It took a while to boot off and on, but it didn't forget my bluetooth or VPN settings like it should have so IDK if it worked. Are we now supposed to contact Apple? Speaking of, do other people with this problem have any VPN profiles as well?

Tried it again after cooling my iPhone by the A/C. Minor improvement: WiFi can be turned on, but the settings for it are really slow and it's not detecting any WiFi.

Sounds like a trip to the Genius Bar is the next step.

Chilled it more and tried again. More success. Not sure how long it'll last though.

But what's the cost for repair or replaceemnt of an iPhone that's almost 2 yearso old with no special warranty?

Out of Warranty replacement is $199US for the 4S. Apple does not repair devices.

So I guess for a 4S owner the cost of iOS 7 is $200, not $0.

No, that's not accurate. Millions of users have upgraded, only a small fraction have experienced issues.

Unfortunately the hardware in your device was flakely and installing an iOS update was more than it could handle.

If they made a flakey phone and pushed out a buggy update they should at least provide the ability to wipe the OS and install iOS 6 again. I mean I love the improvements but basic functionality comes first.

Meanwhile, I haven't had to do another network settings reset and the WiFi functions. I've been trying to go easy on the phone though. I even rebooted it successfully (major problems before with that too) and temperature might have been a factor (even though it had worked fine when being much warmer under iOS 6). My WiFi connection has been disconnecting and reconnecting quite a bit though and there was a point where it seemed to freeze in system prefernces and nothing was working until it suddenly tried to do everything that I'd been pressing in a frenzy (possibly though just general iOS 7 bugginess). But WiFi continued to be enabled. I put the device in Airplane mode for now.

Electronics fail.

Based on the logic above, they would have to replace devices where the Wi-Fi failed after updating to a version of iOS6. That didn't happen because no hardware manufacturer can determine in advance when hardware will fail.

Well even if the WiFi stopps working it's not the end of the world for me, I'm mostly through my contract and was going to dump AT&T for T-Mobile soon anyway, so it's time for a switch.