If you are thinking about seeing any of the towns museums or the Reichstag you are probably not going to have enough time or you will be missing something else on the way.
We walked around town and asked to avoid the bus ride from the arriving train station to the meeting point. This wastes a half hour and allows doesn't give you the chance to see the East Side Gallery. Now, the train's arrival point is apparently not the same for each cruise. You will find out that information on the train. There is a guide on the train that preps you with a map. The train is not air conditioned but with all the windows open, we were fine and it was quite warm outside.
On the way coming back, they supplied a nice little bag of food that was more than I had imagined given the description. We had a sandwich, stick of salami, peanuts, apple, and cheesecake. These are package to all be eaten by hand so the cheesecake may not be the traditional look you were thinking.
The old town had a look of Amsterdam to it. Very nice city. The tour guide was an interesting character. Silence is appropriate as tour guide, not everyone needs to see each McDonalds and KFC that is in town.
John Lawrence is on the ship giving you tips which are very useful. His video is played on tv if you can't catch his presentation and his information on tv had more to offer sometimes. He offered the public transportation advise.
St Petersburg is going through major restoration. We took a private car to see both Catherine's Palace and Peterhof. We saw them extensively. We heard from some that took the all-day tour that they didn't get to see all the fountains on at Peterhof because they were there too early. You should also know that pictures are not allowed in Peterhof but they are allowed in Catherine's Palace. Not sure why because both had the same types of interiors.
The next day we took two tours; the Hidden Scenes Walking Tour and Venice of the North. Both were interesting, but the only thing that was annoying was that both ended with the last hour at the same shopping area near the Church of the Spilled Blood which didn't offer very good prices at all. Before going on this cruise, we were in Moscow and found the prices to be substantially better there.
Stockholm was beautiful city. Walking into town wasn't that long and you didn't buy much additional time taking the shuttles because you had to wait for the others to get on. It also drops you off in the center of town not giving you a great way to circle the town.
We started by walking to the Old Town. From there we walked to Town Hall and took a tour (required) of where the Nobel prizes are announced. We then walked around town and had lunch. After lunch, we thought we would go see the Vasa museum but that proved to be impossible. While we made it to the building, the line was incredible and we only had one hour before we had to get back.
For our first port, we were disappointed in the lack of time for this city because there was more to see. Ideally, another two to three hours would have made it perfect.