I worked at McD's for about 5 years though highschool and college. As soon as I turned 18 I was made a manager and by the time I left I had trained 2 assistant managers, was in charge of the morning deposits, as well as payroll and a bunch of other things (and had to train 2 more managers just to take over everything I was doing LOL). On top of that, my franchise created a scholarship program for managers at my store manager's request. It was only $500 a quarter but that paid for books and supplies.
So while people may look down on people that work at McDonalds, and some stores are incredibly crappy, overall it's a great oppertunity to learn real life business skills if you have the ambition to move up. And even then, some people are honestly happy working there.
