Anyone who has used Apple Pay can tell you how simple it is to use. You place your phone next to the payment kiosk, put your finger on the home button, and you're done.
It's not the fanciest of apps. It has a map, with custom icons placed atop businesses where you can expect to use Apple Pay. Tapping on an icon will reveal the business name. When viewing details about a business, tapping on the eye icon will bring up a screen where you can indicate if Apple Pay worked, and rate your overall experience at the business.
Furthermore, the app offers the ability to create an account and add new businesses and locations to the map as you discover them. Think of it as a way to crowdsource all of the locations where Apple Pay is accepted.