Pretty good, although there was a bit of a surprise, they provided a free cushion to solve the problem

I rented from Europcar and my friend rented from AVIS. At Europcar, there were staff at both the pickup and drop-off points in the parking lot. However, at my friend's rental company, sometimes there were staff and sometimes not. The guy at Europcar in Frankfurt train station was great, very enthusiastic, and did not try to up-sell anything.

The available car models online did not match the ones at the physical store; everything else was fine.

They didn't notify me in advance that the reserved model was not available, which is not user-friendly.

I booked an Audi A4 wagon, but they gave me a Mercedes E220 wagon instead. Very satisfied! Picking up the car was just a matter of completing the paperwork at the counter and following the staff's instructions to get the car myself. Returning the car was even simpler: I handed over the keys at the counter, was asked if the tank was full, and was told everything was fine without them even checking the car. I picked up the car 2 hours early and returned it 1 hour late. No problem. Germans are so trusting and accommodating. Highly commendable!