After 8 cruises on different Carnival ships, we decided to try Norwegian. Carnival's food is a little better (especially the Guy Fiera burgers); other than that, everything was better on Norwegian. We had a mid-ship balcony on level 8, and it was spotless and spacious compared to any Carnival ship. Service was of course impeccable. Very easy boarding and self-assist disembarking. The first day was very chaotic once onboard, with elevators being hard to come by, but that's pretty much always the case. The bars on Level 15 were horrendously crowded the first day, and we had to wait in line for 30 minutes or so to get a drink. That was much less of a problem for the rest of the cruise. If you want to see a show, be sure to make a reservation, or you won't get in. Also, pack your patience to get on the tenders, even with a reservation. In my opinion, Norwegian Epic is a great ship and an excellent value.
The shower was HUGE compared to Carnival's. The balcony was twice as big as Carnival's, and we did not have the oversized balcony. It was spotless, but as far as that goes, Carnival was also spotless. Joelix was our room steward, and he amazed the 3 of us by remembering each of our names during the whole 7-day cruise.