We enjoy difficult puzzle caches very much. We've placed one, of moderate difficulty, and those who have figured it out without a clue really seem to enjoy the feeling of accomplishment.
A difficult puzzle, a la gcnfkb, provides a pleasant diversion in the comfort of your home with your choice of music, beverage, and company. If it is solved, great! If not, well, the mental exercise might forestall the onset of dementia!!