The shuttle drivers and booth workers are usually professional and courteous. We have never had to wait for a shuttle to take us to the airport or to pick us up from the airport. Although they aren't the least expensive park service in Tucson, they do have a reward program that pays for itself if you use it often enough. We are very pleased with their service.
Place was full probably because of college graduation weekend, but my reserved space was ready for me. Shuttle was there moments later and I was whisked to the terminal. The return was just as fast.
You are there 24/7. I had a problem in another lot, where my car was no. 5 hit by a vehicle that 'lost its brakes'. Fortunately, that was also a place with 24/7, so the police were called. However, the last time I used that lot, no one was at the front office, which made me quite nervous about the previous incident. At the public lot, there is not someone 24/7, I don't think. An accident there and the customer is just stuck for the repairs.