I guess opinions vary. Give me the best lie-flat seating that gives me undisturbed (and undisturbing) access to the restroom and I'm pretty good. Some 1st class configs also give a greater level of privacy. An 18 hour flight is long and boring and I suppose an old-fashioned 747 lounge would be nice but I really have no interest in a gym/shower. (And honestly gym options on a plane seem pretty problematic.) If I had that space to play with personally, it would definitely be a nice cocktail lounge/dining area rather than a gym.

Maybe if this were something I was doing all the time but as a sometimes event, comfortable sleeping and entertainment options (which I can mostly handle by myself at this point) work pretty well.