No waiting time as compared to the airport. I flew to Madrid airport, but instead of taking the car there, I decided to try this time in the city, so I could combine it with a visit/lunch.
At the office I was lucky, as the car that I booked was not yet ready (I arrived a bit earlier than planned), and I was offered an upgrade to a car that we really enjoyed driving. No additional fees for driving to Portugal (which we didn't do in the end). I took their CDW.
Easy to arrive, get the car in a parking next to the office and returnign it to the same place. No problems during the rental (8 days).