Nice initial desk guy tried to sell me on upgrading my rental to a new category for €20/day extra, but my rental was just €16/day so I have no idea why he thought I would want to do that. Perhaps he meant an extra €4/day and he just misspoke. I had to tell him twice I wanted the car I reserved. Interaction was super quick though, over in 3 minutes.
ound the car pretty quickly but noticed there were 3 damages not recorded in their system. With the help of the return desk woman she entered them into the system. However she would not enter in a scratch next to another scratch when I asked her to, so fearing this I took a video recording of their entire car. When I turned in the car the gentlemen doing the return had marked it as a new scratch, but once I showed him the video he made a note that I had photos and the scratch was already there.
One major setback was that my car was keyed while parked in the Santa Justa trainstation in Sevilla, and I can only assume because the car has SIXT logos on it. My advice to everyone is to put a local newspaper or something like that in the car and cover up the SIXT logo if you have some convenient way of doing so. I also always take a photo of my car where I park it just in case, and I reviewed that photo and determined I was not parked too close to someone to cause that hostility. I'll never know for sure but that's my leaning anyway.
Overall this experience was consistent with previous car rentals, and I will use SIXT again in the future as I feel their employees have integrity, are friendly, and provide a good service.
I have yet to receive the bill for the key marks, perhaps it will be absurd and I will edit my review if it is.