IPhone IOS Wi-Fi issue fix
*UPDATE* Apple came out with 8.1.2 but it still has not fixed all issues. 8.1.3 has come out and fixes a lot of the know issues; including wi-fi.
With the new IOS 8.1.1 that just came out it was stated on a few websites that the wi-fi issue is still buggy. If you are still having a problem there is a fix below that will help you until Apple can resolve this issue.
You need to disable Wi-Fi Networking Services. It will be under:
Settings > Privacy > Location Services > System Services. Go down to Wi-Fi Networking and turn it off.
Next you need to reset your network settings.
Settings > General > Reset and tap on Reset Network Settings. The phone will reboot.
This will not turn off your Wi-Fi.
More Fixes below(click on Picture). Do them only if you are having a problem.