I used it for a car rental. Big mistake. The price was too high, which I did not realize until I used the app again to reserve another car and what was displayed was different than the final screen, which contained the final amount. It was thrice the price. I tried to cancel it right away and although it was less than an hour after the booking the app wanted to charge me almost $200 dollars to cancel. I was fortunate in that I was able to contact a human being at Rentalcars.com and that person refunded the entire rental amount.
In addition, the first rental I booked using the app I was quoted $264, way too high, and the rental car agency charged an additional $300. My first mistake was to think a four day rental was worth $264 and secondly to rent from Budget Rental Car. Their fees and options are a pure "rip off." Never will I use Budget or the Rentalcars.com app. I am finished!