I am a Santa Fe photographer working on a lenticular series called World Waters, so far from the US and Alaska and Europe.
We arrived on the Celebrity Constellation, and the boat docks a short clearly marked walk from customs clearance-- perfect location! But the pilots are very casual: they do not secure the boats to the dock, but simply keep the motor running towards the pier. This is REALLY a hop on hop off in that they left the pier as soon as passengers disembarked and before we had a chance to do our hopping on! I had to wave my ticket (flailing arms!) to get them to see that we needed a ride; too casual. Stops are at all the places you'd want to see, and since we had such a short day there this was the perfect mode of transportation for us. They do stop at the Vasa, and this is a big plus as it it a bit of a long bus ride to get to in on land; easy by boat. Price was wonderful considering how expensive Stockholm is. Perfect ride except for the jockey pilots.