Apple says it's pulling back the update as it investigates the reports. The company says it plans to issue advice to users "as quickly as we can."
However, if you are amongst those that upgraded to iOS 8.0.1 and are now experiencing issues, that's of no help. Fortunately, there's a fix for you. Most users are reporting that downgrading back to iOS 8 fixes the issues. Here's how you can do it.
You'll need to connect your phone to a computer running the latest version of iTunes, and then download the iOS 8 image file corresponding to your device. Right click on the link and download for iPhone 6 and iPhone 6 Plus. While other devices haven't reported this problem, you can get the corresponding file for your device here.
Download the file corresponding to your device using the links above. Connect your device to a computer with iTunes installed, open iTunes, select the device and instead of clicking on Check for Update, press the Option (Alt) key on your Mac and then click Check for Update; or if you are Windows, hold down Shift before doing the same.
Point iTunes to the file you've just downloaded, sit back and follow the iOS 8 upgrade instructions as usual.
Update: Apple has posted an official fix, which consists of exactly the same steps we recommended above.
Did this fix your problem resulting from iOS 8.0.1 update? Let us know via the comments.
Written with agency inputs