The ease of use, and the customization which allowed us to create multiple different programs without too many headaches. Nothing. Just do it! The app is very intuitive and easy to use. The only thing I can think of is that the customer support could be more detailed. I'm just trying to understand the ins and outs of the app. Make sure you know what you are doing. The fact that it is so easy, and intuitive to use, made it easy to make adjustments in the middle of the process. We are using Loopz for a mobile payment program for events. It is very easy to use, and gives us the flexibility to have multiple different programs.