We used them in Germany a couple of years ago. At the airport pickup they didn't have time to show us how to use the GPS as we requested. We never did get it to work.

When we returned our rental I knew we had a problem when I observed the folks ahead of us having the closest inspection of a rental car I have ever seen. I was right. They found damage on our car as well as the previous car. We know we had not done any damage during our two week rental.

We fought the charges with the credit card company (AMEX) to no avail. To make a long story semi short, we are deep sixing Sixt.