The customers can be very rude; but depending on the roll of the dice, your manager can be even ruder--such was the case with my experience. It was my first job and my manager basically insulted me the whole time, so I quit after 2 weeks.
Also the food service itself can be very stressful, especially when having to do rushes by yourself, which you will have to do within a few weeks of working there. What's so stressful about it? Well that's having to make every single sandwich while dealing with a pair of eyes watching your every move (and mistake.) At least at McDonald's you don't make burgers in the front.
Basically, with this job you'll either pick it up and do okay (if you have past fast food experience likely) or you'll fall horribly behind. But if you are considering this for your first job, look somewhere else--the perks are not worth it.