We just returned from an absolutely wonderful cruise of the W. Med.
I built in a day in Rome both before and after the cruise, which gave us time to decompress from the long flight and to see the sights of Rome.
Because of NCL rules regarding cabins (must be a 21 year old in every cabin), we had to all be in one cabin. This caused me a lot of stress beforehand, worrying about being crowded, where to put clothing, suitcases etc. This all turned out to be no problem at all..there was more than enough room for us all. They made the bed into twins, the couch made a very comfortable bed, and another bed came down from the ceiling that the 18 year old claimed for her own and loved sleeping there. Even when it was pulled down, there was plenty of room to get past it to go out to the balcony and to sit on the couch to watch soccer games on tv. Despite many naysayers, we all liked the separate shower/toilet/sink idea and none of us felt the frosted glass walls were an issue
The kids loved the Teen Club, Blue Man Group, Cirque, bowling, rock wall, gym, etc etc. They also really enjoyed the food...we never ate in a specialty restaurant and found the food more than adequate. I would hate to guess how many ice cream cones the two boys ate in the week!
Were there some "issues"? Yes, of course there were. With four people(1 set of siblings and two generations) there are always going to be a few. But we went into it with the attitude that if one of us got stressed, the others would give them time to work it out.