You should have an enjoyable cruise. Trying out a new cruise line is always fun. It's hard not to make comparisons to other cruise lines, but try to stay open minded. The Pearl will have some unique features unlike the other ships you've been on. IE: the bowling alley. The Freestyle dining will be a new concept for you. Most people either like it or not. I have found NCL is very comparable to RCI and CCL. However; I do notice differences particular in entertainment. I've been on NCL six times and what I notice most is their production shows are lackluster. I'm not saying the show itself is bad, or the talent of the young dancers and singers. It's just the costumes, stag props, and back drops really lack. To me, that can really add to a shows excitement. Another area I've noticed is the buffet area. The quality of food is good, but the choice of selection lacks compared to other cruise lines. Trust me though, you will not go hungry. I also think the buffet area layout has been awkward on some of their ships, causing congestion in that area.
Overall I think they are a good product for the money. I haven't been on the Pearl but hear it's a beautiful ship. Have a great time.