I have used Thrifty off and on. They are at fewer airports than others. A mixed bag. Many locations have off airport facilities that are further away, which can lead to longer time to get car. In ORD, (a while since I used) one needs to go to the "bus/hotel pickup area" which is a 5+ minute walk from baggage claim. I am Blue Chip and sometimes contact is not ready to go, other times fine. As Blue Chip, they give me an upgrade about 70% of time. Check in is not "at your car" - so a bit longer. And as they have fewer renters, shuttle service ususally not as frequent. Mileage credits are pretty good with some partner airlines (US Air promotion, for example). Cars may not be as new, but I have not got a real dog.

They have the PT Cruiser, but more expensive than other cars.

Overall, if not in a big hurry and occasional less than excellent service is ok with you - worth the approx. 25% lower rates in most areas.