This was my first NCL cruise, while I generally enjoyed this cruise and the tours, there were just more "hiccups" (some more serious and inexcusable than others) on this trip than I experienced on any other cruise lines. Consequently, I doubt if I will consider an NCL cruise again.
Dos ...
Spend extra time in Barcelona. It is a super city. Visit to Sagrada Familia.
Shower-sink-toilet arrangement on Epic is atypical and widely criticized. It is however manageable. Cabins are very tight and extremely difficult to maneuver from one end to the other when more than one person is dressing and/or selecting their clothes.
Barcelona is a super city. Great Dining. Reasonably priced. Easy to get around, Visiting the Sagrada Familia is a must. We also enjoyed the Gothic quarter. I plan to return to this city in the future.