I ate at the (only) McDonald's in Beijing when I studied in China in 1993. At the time (this may still be true; I'm not sure) it was the biggest McDonald's in the world. It had just opened the year before. I don't remember much about the food, but I do remember it was packed with mostly Chinese people (not many foreigners in China in 1993, even in Beijing). I didn't go for the food (I rarely ate at McDonald's at home and wasn't missing American food too much at that point) but more for the kitsch factor. I only went that one time.
I think that was the only McDonald's in China at the time, but I remember seeing LOTS of KFCs throughout the country (don't think I ever ate at one). They also had Pizza Hut.
As for eating fast food on vacation, our first stop after the airport on West Coast trips is In-N-Out if we can swing it.