I have studied the Enneagram for many years and find it to be amazingly reliable when used properly. Recently, I'm hearing that it is now used in businesses to determine people's fit for various jobs. I don't think that is the most helpful way to determine that. The Myers Briggs is much better or, especially, the DISC model. In business, it's not necessary to understand the underlying motivations of people.
However, for an individual, when used by a professional who understands the Enneagram, I think it can be amazingly helpful for them to understand their deeper selves so they can live happier and more fulfilling lives. It can explain many of the unique things about a person that they might not understand otherwise.