Trying to remember my experience at Avis STL recently. I think the app worked and I was assigned an Cadillac XT4 (not world-class but an okay rental car). The issue was that I wanted to add a designated driver onto the car and that took us into the counter. Fortunately, we got in line quick as a few people were behind us. I can imagine how slow it is if there are a lot of people waiting.

I don't think Avis tech works very good. I had an HNL reservation and it wouldn't give me anything on the app so went to the Preferred booth and got to choose, but glad there was nobody in line.