I was on the 6/20 Magic sailing out of NY. Embarkation was awful but I learned some tips and tricks from other guests to avoid it. Try to get the earliest embarkation time. If you don't, the wait gets longer. We waited 2 hours from arrival to walking on the ship with a 12:30 embarkation time. Other people told me the waited only 30 minutes arriving as early as possible.
Capacity was high. The number we were given was 4500 people (not sure if this is just guests or guests plus employees). There were a lot of kids so I wouldn't be surprised if we were over the standard capacity. We were never able to find an open seat on the pool deck, and there was no enforcement against people hoarding chairs with towels without showing up. We had trouble disembarking, tendering, and getting luggage tags due to the high capacity.
The entertainment was wonderful. We had the late dinner and usually go to bed early so we missed a lot of the stage and comedy shows but what I heard was hit or miss. We did go to one comedy show and we somewhat liked it but it was too PG for our tastes but we don't knock the comedian for this as it was a PG show. We enjoyed all live bands, orchestras, and musicians we heard around the ship. If you like entertainment I would not recommend choosing the late dinner as it often conflicts with many events (unlike the early dinner).