I think it's a usability problem with the app - you can't easily see how much the trip is going to cost. It's actually not even completely apparent that you've booked a trip. The app should be redesigned to always show the quote before booking and a very clear button that says "Book Now". The pickup location UI could also use some work - the GPS isn't always accurate and noticing that it's wrong and changing it isn't very intuitive. But apart from the problematic app, I've found the service itself quite impressive - somehow they always manage to find me and it always ends up costing less than I think it will.