Great experience with Sixt. The nice thing about them was that the third party liability insurance was included in the rate I booked at. They asked if I wanted to purchase additional insurance. When I said no they did not push the issue and did not try to upsell. There was no wait at the counter. Wait for the shuttle was also minimal.
Only negative is that the car was not new and it showed. Car had 55,000+ miles on it but I had no issues with it. They will take a large deposit on your card but you will get it back.