Did the Princess tour to the ski-jump (not so great), the Viking Ship Museum (well worth it) and the Vigeland Sculpture Park. The tour of the park made the day and the trip to Oslo...absolutely amazing.
Skipped the trip to Berlin as we will be doing an auto tour of Germany etc. in the near future. Glad we did as the train was several hours late returning to the ship as they "lost" two passengers in Berlin. The trip to Lake Schwerin, the castle and the town were all excellent, as were lunch and the walking tour of Rostock on the return to the ship.
Joined 8 others on an ALLA tour using the Cruise Critic website. Brilliant. There is so much to see and even two full days only felt like we were skimming the surface. I think being in a smaller group (and in a smaller shuttle bus) helped immensely in getting nearer the front of the line and getting through the city traffic (awful especially during late afternoons). However, Saint P. was the highlight of the trip by far and the best tour guide, our small group and the tour program made it even more so.
A short stay, it would have been great to have another full day to wander on our own. The Vasa Museum and City Hall were first rate, but would have loved to have another day just wandering through the old town, taking a canal cruise etc.