Great reservation process (I worked with them via email for one of the "guaranteed models" from their luxury line). My point of contact was Sr. Luxury Fleet Agent Verena Rechner. Verena was incredibly responsive to my requests and provided outstanding service. The pickup and return process were smooth. The vehicle itself was almost immaculate and as close to being "new" as I have ever had for a rental.
Unfortunately there was an error on the billing. These things happen. It took a few emails, but Customer Service ultimately made it right and I am satisfied with the post-rental support.
This was my first experience with Sixt, and I will be using them for all future trips to Europe. I also learned that they cover a few cities in the US, and I will certainly keep that in mind. It is incredibly satisfying to have a "guaranteed" model as your rental.
4.85 STARs (97/100) A+
Very highly recommended!