Cargo ships have very limited numbers of cabins they sell to passengers. The article hit most of the information. Dining is in the mess with the crew, which is usually fun and interesting.
One potential problem is that cargo ships often have to alter their schedule and/or itinerary mid-cruise. Delays in picking up or dropping off their cargo occur with regularity, or they may get a call from the boss, saying they need to go to a different port next to pick up new cargo for a new contract.
It's best to be laid back and go with the flow when cruising cargo ships.