Apple released iOS 8.0.1 update a few days back in order to fix the serious bug issues in iPhone 6 + Apple devices, you can read Top Serious issues and Bugs of iOS 8 here. As the iOS 8.0.1 update is released to fix the issues of iOS 8, but this new update iOS 8.0.1 messed up and created many problems for the Apple users.
WIth the latest update to iOS 8 ( iOS 8.0.1), users can’t use their phones, or they can use the Touch ID, several network connectivity issues has been reported while using iPhone on multi cellular networks and even after restarting the iPhones they are not fixed, the devices keeps on switching into Airplane mode if we try to reset the network settings, we need to use the Touch ID for many things like validating our identification in Apple store and it is used in many internal apps, but it has been disabled by the new iOS 8.0.1 update, If we try to use that feature, it displays a error message saying “APPLE’S WORKING ON A FIX, BUT IT’S NOT HERE YET”

So how to revert back or downgrade from iOS 8.0.1 to iOS 8 ? here is the procedure to downgrade to iOS 8 ( Thanks to RENE RITCHIE )

You need iTunes installed PC or MAC, your iPhone or Apple device which you updated to iOS 8.0.1, USB cable and yeah internet connection to download the firmwares
You need to download iOS 8 firmware which you can find ipswdownloader.com. just select the device name and select the model and it will display the firmware for your Apple device
Here are the direct download links for iPhone 6 and iPhone 6 Plus
while you are downloading your firmware to your MAC or PC, you need to go to Settings > iCloud > Find My iPhone on your iPhone and turn off the service, for that you need to enter the credentials like your Apple ID and password
Now connect your Apple device, here I am using iPhone, open up the iTunes and at the Top right you can find the iPhone tab , click on it

After that click on “check for Update “

Note : You need to press the Option key (if you are using MAC) or Ctrl key ( On windows) to display the update

It will display a window where it asks you to select the firmware ( .ipsw), there you go select the file you downloaded in earlier step from ipswdownloader.com and click OK
Now your device will be restored to original iOS 8 rather than iOS 8.0.1, and none of your settings or data will be erased or changed, just you are downgrading

Still if you are facing some problems in downgrading to earlier iOS 8, you need to try full restore using Recovery mode

source: RENE RITCHIE (TWITTER) | Via : Verge