The office itself has a very nice and ultra efficient staff. All my papers were checked and I got the key to the car in less than five minutes. The online booking is quite simple and very well explained. Works well even if you book via the ADAC page.
However, I now thrice had the experience that car damages were attributed to me or my driver, which in neither case was the fact. The last time the person handing me the car even made comments about the damages that were later said to have been caused by me. In all cases this turned out to be nothing more than an inconvenience, but it still left a stale taste.