Maybe they should have copied Apple's design.

Less successful is Samsung’s take on the fingerprint-unlock system made popular by Apple with the iPhone 5S. Like the 5S, the S5’s home key features an integrated fingerprint scanner, which can be used to unlock the phone or authenticate purchases online (Samsung is partnering with PayPal to enable this feature, though it doesn’t validate purchases from the Google Play Store). Samsung’s version requires a vertical swipe over the home button to activate the scanner, and we found it to be quite unreliable and virtually impossible to activate when holding the phone in one hand. It can store up to three different digits, but it was very particular about the speed and orientation of the swiping motion used — if we weren’t doing a perfectly straight swipe down, it would refuse to unlock the phone.

Speaking of Apple's iPhone 5S, that Touch ID home button is holding up pretty well for me. I get the occasional rejection, but nothing that detracts from the convenience of not having to type my (long and pretty secure) passcode. I like the idea of integrating with PayPal, though I'm guessing Apple has its own idea about how it'd like to do payments.