I really do not like these articles that say "science says not to worry, you must be a very stupid and uneducated person to be worried about this." Any honest scientist will tell you that science does not know exactly how the human body processes food and there is no model which will exactly predict the effects of the human body ingesting a certain food.
Saying that the experimental results are mixed does not make me feel better. Experimenting with humans is very difficult, and certain types of experiments are downright impossible. Thus, effects of foods that do are not immediate and drastic are very hard to determine in human experiments.
Think about a food that we now know is very dangerous: trans fats. Humans had been eating trans fats for about 80 years when they were definitely found to cause heart attacks. Only then there was enough data to make a definite connection. And while there were some scientific articles that suggested a connection in the 60's someone could always say "there is no definite proof." Many people died of heart attacks before the statistics became such that a connection was obvious.
Then there is the tendency of people to wrongly assume that compounds that are kind of similar will have the identical effect on the body. Thus, for a long time carbohydrates were all bunched together because they were very similar molecules. People would often say that carbohydrates cannot be bad for you because humans have been eating rice and wheat for centuries without negative effects. But it turned out that fructose is a little different than other carbohydrates and it can be bad for you.
And then there is the fact that the same thing can be benign or very dangerous depending on what form it is in. Thus, fructose is absolutely benign when eaten as part of a fruit or vegetable, but quite harmful when eaten in a refined sugar or high fructose corn syrup form.
So I am very very suspicious of any food additives. The only rational decision for a human being is to eat the type of foods humans have eaten for tens of thousands of years before and for which our bodies have evolved. Maybe MSG is benign. Or maybe it is actually bad for you. I would prefer not to become one of those statistics that allows scientists to prove many years from now that MSG is indeed bad for you.
MSG is especially worrying because there are some studies that show negative effects of MSG and the fact that other studies show no effects does not quite negate these. Furthermore, I myself feel negative effects when eating certain foods that I suspect of containing MSG.