To be honest, I was quite leery booking with Sixt at the airport in Wroclaw, especially after reading a number of negative reviews. However, the price the offered for an SUV was so much lower than the other carriers, I decided to take the risk.
I'm glad that I did. The service that I received with Sixt was fantastic. The staff who worked at the desk were very friendly, courteous and professional. Unlike a number of people whose reviews I had read, I had no problems with the reservation. I had remembered to bring my rental code from the 3rd party website I had booked through, as the website suggested. But, as it turns out, I didn't need it. The staff new I was coming.
Another issue many people have raised had to do with insurance. I had purchased rental insurance through CAA before we left. I was a little concerned that they wouldn't recognize it, but again, there was no problem. I showed them my insurance certificate (which CAA strongly suggested I do), and there were no problems at all.
Once we received our keys, we went out to the parking lot and found our car. We were met at the car by someone from Sixt who did a walk around to ensure there was no damage to the car. This was another area of concern for a number of people, but it wasn't an issue for us. We mentioned a couple of spots where we saw dings, and scuffed paint, and the employee noted them.
The car itself was great. It was big enough for the four of us, super comfortable, and performed very well for all 3,000 km we drove during our 3 weeks.
I know a lot of people have posted negative reviews, but our experience with Sixt was nothing but positive. I will have no problem renting from them when we visit Poland again.