I thought it worth the read because long term, elevated levels of cortisol, and their effects on the body, are well documented. It's usually not addressed until it reaches Chronic Stress, which has nothing to do with Cushing's or Addison's disease... but is quite damaging in and of itself.
I recommended it as a good read on understanding adrenal gland function, and the effects cortisol can have. Even slightly elevated levels can wreak havoc... regardless of what you call it.
I appreciate the Mayo Clinic's take on labeling adrenal fatigue as an unsubstanciated disease; I think they happen to take it a bit too far in its dismissal of cortisol effects.