I did a 14 day cruise in the Med on a similar vessel it was like working on the oil rigs only you didn’t get paid, food was pub grub style, if you wanted better quality you paid extra. I paid a Service Charge upfront then paid another on any services onboard. After enquiring why, the upfront charge was for the behind the scenes staff. Whilst the vessel was huge it was very claustrophobic inside, entertainment was second rate, the swimming pools area couldn’t accommodate all the passengers obviously. Ok we had daily various ports of call but you were continually clock watching and didn’t want to venture far from the port in case you got lost and missed the boat, they didn’t hang about. The most boring part was the 2 days at sea returning to the home port, nothing to do and all day to do it.
All in all a waste of money yet some people swear by them, no idea why.