My favorite is when they tell the Model 3 owner that the Model S is the better car, so you should be happy yours is in the shop - you are getting to drive an S! My experience with S loaners is they are very rough and not loved, so big dents, dirty insides and smelly ACs. Unless you get the Enterprise rental S as the loaner, then it is new, but also doesn't have TACC! And you don't have app access to the loaner, so no preheating, not knowing charging status at the supercharger, etc.
First world problems, but normally I just want my own car back.
We actually no longer take the loaner when we have our S or 3 down for service. It is just easier to drive our extra ICE pickup instead and not be tied to Tesla's schedule to pick the car up when it is done. It is 2 hours from our work to the nearest SC, so arranging to take off time on short notice to pick a car up before 6 is a big hassle. Especially when they will tell us the car is ready, then call us while we are driving down and after we took off work to say "just kidding, come get it tomorrow". If I am not in their loaner, I can just tell them I will pick up on Saturday at my own leisure.