I have used them a bit and they take your money but zero service when it gores wrong - i rented an Alamo/Guerin at Lisbon airport, car broke down and Guerin' service was truly awful. I had to use ubers for a week, I contacted both Guerin and Rentalcars fro a refund as the car had only worked for one short trip and Guerin would not bring a replacement - neither responded. Guerin seem to still think I have the car when it is in the hotel car park where I reported it broken down for the second time and RentalCars just don't respond - i am getting a refund via my card provider - avoid them!