It's a car. You only need it for one day. Get over it.
I had a courtesy Micra once. It was bloody awful, but it let me get from A-B. if image is that important to you, why did you buy a Nissan?
If they spent more on courtesy cars, they'd have to charge more to make up for it. Yeah, it's nice to get exciting stuff to drive when you get a courtesy cat, but it's just that: A courtesy, not a right. It's pushing towards a rights bit more when it's a warranty fix, I will give you that though.