I've been to the McDonald's in St-Avold from time to time, and every time I've had the same experience.
The food is good and hot, but the service is fast—so fast, in fact, that they sometimes forget items I've paid for. Luckily, in most cases, I was able to get the missing item at the register by showing my receipt.
However, this McDonald's is far from exemplary in terms of cleanliness: tables covered in grease, fries on the floor, and so on. They definitely need to improve in this area.
It's far from the worst McDonald's I've been to, but it's not the best either.