Just answered your other thread, on HAL, so I thought I'd post here, too.
I've only done one NCL cruise, with friends who wanted to go out of a port not served by HAL. It was on the Majesty, which certainly was far from majestic. The cabins were tiny compared to HAL (even the one that was supposedly a handicapped cabin). Everywhere on the ship seemed crowded with people. The food in the MDR was mediocre and usually arrived at the table barely warm, and the buffet was minimal and the food there overcooked. The evening shows were poor (we walked out of more than half of them) and before them, as the theater was filling, the staff walked around hawking pull-tab tickets.
I swore off of Norwegian, although many of the disappointments on that trip may have been limited to that particular ship. Now I'm considering giving the Epic a try.