"MobX usually reacts to exactly the things you expect it to. Which means that in 90% of your use cases mobx "just works". However, at some point you will encounter a case where it might not do what you expected. At that point it is invaluable to understand how MobX determines what to react to."

I'm going to be tossing and turning tonight trying not to dream about libraries that usually work 90% of the time.