I somehow get the feeling the fingerprint sensor on the iPhone 5S will be a flop

It is just a gimmick along the lines of Siri. You try it a few times when it is new, play with it and showoff to your friends. Then you forget about it. Nobody I know uses Siri anymore. At least with Siri you can make the argument that it is useful in the car while driving and such, but how many people really use lock screen passwords? I could see some limited application of the fingerprint sensor to bypass password authentication for App Store purchases and whatnot, but then again it is such a narrow application.