We rented a car for 16 days. The lady at the desk was very kind and professional. We weren't bothered with extra insurances or other offers (many people seem to complain about getting offers they already paid for). After 10 mins at the office we got our car. The contract was simple and easy to understand. The car was very clean and in great condition. Also the employee showed us every scratch (only little ones) the car already had and gave us time to see for ourselves - no pressure at all!
The return went just as simple as the pick up. We got our receipt with a confirmation that the car is fueled up and without any damage.
Overall Sixt offered a very professional service without hidden fees or any kind of rip-offs. I totally recommend renting a car here.