A couple of decades ago, everyone had this complaint with Chinese restaurants to the point where many stopped using MSG in their cooking. Subsequent evidence suggests much of the issue was psychosomatic.
I'm one of the few who reacts to MSG if too much is used in a dish. I notice that it only happens at a Chinese/Asian restaurant after I partake of a particularly tasty dish. The thought of MSG does not even occur to me so I don't agree with it being psychosomatic. I just suddenly get a strong dull throbbing and ache in my head that extends down to my neck and shoulders, and I have a very heavy feeling in my chest. I also feel very hot all of a sudden so I sweat and my heart palpitates. I usually have to drink a lot of tea or liquid. The symptoms go away after fifteen minutes or so.
I was totally against MSG before because of these incidents but after reading about it some more, and discovering that MSG is present in natural sources like mushrooms, seaweed, cheese, etc, I've decided MSG is not necessarily bad at all. I won't have any qualms using it in small quantities.
Personally, for me, it is bad. It is the only thing I know that gives me a headache. So I avoid it like the plague. and I use almost no processed foods.
I also rarely get Chinese takeout from the little places in the neighborhood, because even though they say no, they all use it.
The jury is out on the long-term effects of msg. Glutamates that are naturally produced by various foods are not the issue. The chemically created stuff (Ac'cent and assorted brands) are. Follow your own brain.