I am unfamiliar with this product. But we loved a longer cruise in Croatia, but that cruise line went out of business. We loved being moored directly by old city walls, with the place to ourselves after the tour busses left at 5 PM. (Perhaps a true Rick Steves reader would do that by staying in a spare bedroom somewhere .... it's a matter of travel style.) This is a country best seen by water.
I would beware of the mooring in Dubrovnik. We were ... told ... that NO ONE can tie up in the scenic marina in front of the city. Our 30-cabin cruise ship was forced to moor in the commercial port, a bus-ride away from the city of Dubrovnik. Maybe they're small enough to have a special deal. Our ship was big enough to have many organized excursions, like to Plitvice and Roman cities. Katarina looks much smaller.