The little things that made it great: no annoying loud speaker announcements; no pesty bar wait staff; no pesty photographs. If I wanted a drink or a photo, I could easily get it. But nobody was "in my face" trying to sell me anything.
The little things that made it less than perfect: the order of the meals in the dining room. I loved the food, but I didn't want lamb two nights in a row (even though I love lamb) and I didn't want slow-cooked meat two nights in a row (even though I love osso buco and braised short ribs). The cabin steward, who left us Q-tips on Day One but then didn't replenish them. The same cabin steward, who didn't bring us ice at 5 or 6 pm even though we asked for it a few times. The same cabin steward, who left us the old Daily Program once instead of the next day's. The time change -- we wanted to get up at 6 am to see the entry into the Panama Canal. After dinner, lo and behold we find out we're losing an hour's sleep that night! We'd rather have lost an hour after the long Puntarenas day, when we were already exhausted but when we had an AT SEA day the next morning so we could sleep as late as we wanted.
I personally would've preferred going to Jamaica or Grand Cayman rather than Cartagena, after the Canal.