Juli Clover, reporting for MacRumors:
Following the release of iOS 8.0.1 this morning, numerous of users found that their cellular service was disabled, reporting “No Service” messages after updating. Affected users also appear to be experiencing problems with Touch ID, which seems to be completely non-functional.
Apple has pulled iOS 8.0.1 from the Developer Center and it is also no longer available via an over-the-air download.
In short, do not update to 8.0.1!