The NFC chip in the iPhone 6 is restricted to Apple Pay (source: Cult of Mac). Not surprising. The year-old fingerprint recognition technology called TouchID is used for only two things: iPhone 5s unlock and iTunes purchases. With the iPhone 6 you get to do one more: Apple Pay purchases.
This is how Apple rolls: limit the scope and get to perfect as close as possible. But even after a year, Apple is not close enough to perfect with TouchID: TouchID is still far from a hundred percent in recognizing my fingerprints. Every time TouchID fails the frustration of using my iPhone grows.
Apple needs to realize each failed attempt at using Apple Pay will result in a more severe frustration. Every time Apple Pay fails it will be frustrating, of course, but because you will experience the failure in public where people are waiting and watching an Apple Pay fail will also be humiliating.
A perfect Apple Pay experience is dependent on many variables and some of them are beyond the control of Apple, but I can predict with certainty Apple Pay will not always be a smooth experience, because of the less-than-perfect fingerprint recognition performance of TouchID.