How do restaurants cope with things that can go wrong?

This happened to me twice this month. The first time the dish was so salty that I could not eat it. I mentioned this to my service person and she said that it was supposed to be salty. I have had this dish before and have never felt it was salty.
Instead of arguing my point I waited to see if it would be taken off my bill because I 90% was left untouched. The bill arrived without any changes and no supervisor/manager came by to see if there was a problem.
I left the restaurant and went to the company website and sent them my feedback. The reaction:

a) A full telephone apology in 24 hours.
b) a friendly apology letter from the corporate office.
c) A gift check to use in their restaurants.

I am not sure I will use the gift check but because of thier response I will definitely go back to this restaurant.

My next experience is at Ruby Tuesday in the Reston Town Center Virginia.
I was meeting a friend at the Ruby Tuesday in the Reston Town Center ( We actually chose this restaurant because " If its Tuesday !....).

I ordered a "Grilled Chicken Burger Wrap" waited for 30 minutes when the service person came and apologized that the food was taking time since the restaurant was busy ( Half the tables were empty). After 45 minutes I was asked to repeat my order again.

I am sure like all restaurants there is some room for error but there were several other things that compounded this :

a) I was not asked for my choice of a side dish ( I got creamed cauliflower and only then realized the order would include a side dish) I would have chosen something else if I had been asked.
b) When the food came the service person said the manager would come and explain the delay to me. ( he did not come)
c) My friend and me paid using two credit cards and after 10 minutes the check was brought back to ask how it was to be divided between the two cards.

My theory is that the service person was new. My regret is that I was the subject of their training class and did not enjoy the meal. I am sure this experience is an exception and just want an assurance from you that this will not happen if I go to another Ruby Tuesday.