Update: iOS 8.0.2 is available. Remember before updating your iPhone, backup to iTunes on a PC or Mac.
There is a workaround for those who have lost cellular service and use of Touch ID after updating to iOS 8.0.1 on iPhone 6 and iPhone 6 Plus.
Apple have pulled the iOS 8.0.1 update from their servers and are working on a proper solution soon to be released in iOS 8.0.2.
The workaround is a guide to revert back to iOS 8: http://support.apple.com/kb/HT6487
If you are affected by this bug and need assistance, we can do this workaround via remote support for only $59.