I find Sixt in general a very professional company, everything goes smoothly, I had no problem with them. And I also like to get free upgrade because the upgrade car is usually better. This time I also got an upgrade, but now it had some tradeoffs. I had a Jeep instead of a car of the category Opel Astra, and like I said better car, better experience. But what I don't like that although the upgrade itself is free, this car consumes way more fuel and it means some extra not so insignificant expenses what you have to pay yourself. And in addition to that if I'm right the car had still winter wheels on in August that also suboptimal.