This was our first experience, both with Emerald and with a super Yacht. The ship is lovely. The cabin was well laid out and comfortable. I read previous reviews about the staff and found ours to be less than the superlatives I've read. With a couple of exceptions, the wait staff were efficient but did not remember names or preferences. Some were not even approachable -- efficient, but not personable. Our room stewardess was new and efficient, although the night before we disembarked I found some items (new drinking bottles for the group coming on) in the empty drawers (we had already packed) rolling back and forth to wake me up. The food was prepared well, but if you didn't choose the selection of the day, you could get tired of the 5 or 6 offerings that were standard. I definitely would not suggest buying a drink package since it only covers times outside of lunch and dinner and we could never drink as much as it cost.
A big plus for us were the washers and dryers on board (for free). Since we travel light and had a week in Europe before the tour -- that was a lifesaver.
As for dress, many said there was no need to bring fancy clothes. Well casual is not what I saw at dinner. High heels, dinner dresses (short, not formal) were quite common. Only a few of the men brought jackets or blazers, but the women -- that's another story.