Worth getting up early to see all the beautiful islands on the way in. If you want to see the Vasa Museum (you must!) and generally walk around the old town, on the quayside where the boat docks there is a small shack where they sell a ticket for the small boats which go round the harbour, one of which includes entrance to the Vasa at a discounted price. The extra advantage of this is that, having bought your Vasa ticket, you don't have to join the long queues at the museum and can simple walk in via the 'groups' entrance.
This is what it is all about! Immigration into St Petersburg was much easier than we had expected although it does take time so it's implicant to be ready to go when the ship berths. We did the 2 day complete package with Alla Tours which turned out to be an excellent choice. Only 14 of us with a very good guide. It was amazingly hot while we were there and a slightly better air-con system in the minibus would have been welcome (but overall a minor criticism). The palaces, Hermitage, subway etc were all quite wonderful. A great experience. Tip - if you are wondering about going out in the evening to a 'folk show' you might like to know that a very good local folk group comes on board the ship in the evening and does a couple of shows.
It very easy (and cheap) to get a taxi from the port to the station and then a train to the centre of Gdansk (they run frequently and it only takes about half an hour). So much to see in the mainly pedestianised heart of the place - including some amazing churches.
Interesting, if expensive, city to visit - if only there were more time! The tram system is a very convenient way of visiting the Vigeland sculpture park - return within an hour and you can use the same ticket! Also worth going by boat to see the Viking boats and then the grand cafe and the national gallery which houses the Munch's Scream. Take in the Town Hall's murals before returning to the ship.