Couple things I thought I'd pass on:
1. If renting at airport and returning at a location in Lake Buena Vista, I would ask (many times) the people renting you the car to verify that there will NOT be a "drop charge," which is customarily charged if you return the car to a different location than where you rented it. (I got hit with one of these once when I rented a car at Dulles Airport and returned it to the agency's office at Union station in DC.)
2. The best comparison website I've found for rental cars is breezenet,
www.bnm.com. You can put in your dates, and they'll display for you what each company will charge, both as a daily rate and the net total including all the add-ons. Very useful for comparison purposes between car sizes, agencies, etc.
Hope this helps! By the way, I've rented from thrifty on the previous trips, and had an excellent experience with them even though they're off-airport. In fact, I left my sunglasses in the car when returning and one of their employees found them and tracked me down at the airport to return them to me. Very good service.
Regards,
Joe