I did.
I work(ed) at one and it's the easiest stuff ever. I work the back kitchen (grill, fryer, buns, and table) for like 2-3 hours sometimes and it doesn't phase me. Maybe it's just me?
mcdonalds doesnt work that way anymore son. you will work levels and table for a few hours, then switch over to drive through, maybe do front counter for a few more hours.
and its not the same monotonousness thing over and over. different costumers have different personalities, not everybody orders a cheese burger, and not everybody doesnt modify their sandwich.
although working at McDonald's isnt as hard as being a neurologist, it definitely isnt a job you can preform flawlessly while you are about to fall asleep on the floor.