I'd say off the bat if the customer service/wait times were anywhere near average they would score a 4 or 5.
No one answers the phone if you call and they are busy.
If you want your car "at your reserved time" be prepared to arrive at least a full 45 mins ahead of your reservation time in order to get it in a timely manner. In my case I had a 130 pm pickup time and was not on my way with the car until 230 pm
The wait is ridiculously long....and good luck calling ahead to say you will be in early or at your reservation time as they wont pick up a ringing phone of counter is busy.