Courtsey cars can be a mixed bag, my SEAT dealer was one of the worst.
I hate it that you always end up with a car with absolutely no fuel and either end up spending more than us use or play fuel guage lottery. Not much can be done I suppose otherwise dealers would spend a fortune on fuel. (this applied to all dealers though).
I had an Ibzia FR TDi when my Cupra was in for service which was great fun, made a nice change but I've had other cars that I would be embarrassed to give somebody to drive. They normally smelt of somebodies lunch, weren't clean and one had somebodies garden waste in the boot.
They also kept me waiting 30 mins once as they couldn't find the keys for the car blocking my courtsey car in. In dawned on them just to let me have another car until 2 seconds before they found the keys.
Had a BMW 3 series touring once when my Celica was a week of and needed some paintwork doing, the brakes were shot the salesman said there a bit of vibration on the brakes if you stamp on them hard. Which meant everytime you touch the brakes the whole car vibrates.
My Audi dealer apparently let you have any model you choose as long as they have one on demo and give them enough notice. I didn't ask for anything specifically but got an A4 140 TDi Auto last week which was nice but again not very clean.