Some people aren't too happy with the fingerprint sensor on the iPhone 5-S.

They're complaining it barely works half the time, but there may be a simple workaround. Apple recommends re-scanning your finger or thumb, making sure it's clean and dry... but since Touch ID lets you scan and store up to five different fingers, some users have found that re-scanning your thumb multiple times and telling your iPhone that it's different fingers, increases the accuracy and reliability of the scanner.  

And as always, Apple recommends keeping your phone locked for security and privacy.

--Rob Archer