Been renting from here for years now. Will not rent from anywhere else that a SIXT rent-a-car place exists. Very happy that you can get nice clean top of the line cars with all the features for only a little more than what other place charges for base-model vehicles elsewhere.
Anytime I rent a premium sedan or SUV at SIXT in LA or Seattle, I always end up with a Volvo. The first time that happened, I was a little annoyed, but once I drove it, I changed my mind. I'm happy it happens each time now. When we need more seats, we get a larger vehicle and end up with something else, but either way we're always happy with the car we drive away with. Just be aware that the car you are shown is that "class" of car and not the exact one you'll get. Granted, most places work this way, but some people get upset when it's not what they were expecting.
Also, they do put like a $500 hold on your credit card as a deposit, which is high compared to some other companies, but not uncommon. I'm fine with it since I don't have my credit cards maxed out. Also, don't try to rent a car from anywhere if you only have a debit card. Get a credit card, even if you don't use it much, just for this purpose.
Sometimes it's slow when they get slammed, as with any rental car place, but they have always done a pretty decent job keeping things moving.