I have not dealt with Thrifty in Orlando specifically, but have used them on a couple of ocassions for rentals a while back. I use dthem in 3 different locations about 5 years ago and have refused to use them since. My personal experience is that shuttles are slow, staff is rude, and they will do anything and everything they can to stick you with extra costs!
My last experience was when they asked if I wanted the additional insurance and I said, 'no I don't want anything extra.' To this, he replied, 'so you just want the basic?' When I said yes, he used this as a claim that I wanted 'basic coverage' wrote it into the contract, and stuck me with an extra $20 per day in fees for the coverage when I returned. It was my fault that I didn't read the contract well enough, but he was clearly trying to slide it by, and succeeded with me! I have found this type of behavior and manipulation every time I used them, and simply gave up on it. They have cheaper rates because they hard sell you on insurance and other add-ons.
Again, I've not used them in Orlando, but IMHO, their hassles and manipulation are not worth the savings. I have personally used National every time and been VERY happy (they are right across from baggage claim and if you sign up for their frequent renter service for free you bypass all counters and drive straight out through the booth). If you do feel the savings for Thrift are worth it, be VERY, VERY careful about what you agree to and what you sign!
Good renting...