Gdansk (or Danzig as it’s named in German) is your typical Baltic Sea hanseatic trading town in the mould of Wismar, Lübeck or Riga. The unfortunate distinction Gdansk has is that it suffered heavily at the end of World War 2. The Poles made great efforts rebuilding the city, but as soon as you venture a bit off the city core the gaps are noticeable and the quality of the buildings deteriorates.
The town is quite popular with tourists. Baltic Sea cruises will stop here for day trips. Even on a rainy and cold April evening the town was rather crowded. As pointed out by Bojana getting a restaurant table can be quite a challenge.
A bit North of the city center are the shipyards where the Solidarnosc movement started and the first cracks in the communist system started to show. You can visit a few of the historical places and a museum to get a grasp of what simple workers were able to achieve by means of peaceful protest and strikes.
OUV
Looking at the history of the site with Unesco it feels like Poland already decided to make it a former tentative site, but never handed in the paperwork. If you get a negative review the first time and then ask not to be examined the second time, inscription chances look very slim.
I do agree with Ian that the subject of Baltic Sea hanseatic trading town is already well covered by sites such as Lübeck, Wismar, Stralsund in Germany, Riga in Latvia or Torun in Poland itself. While today these sites span three countries and nationalities in medieval time there was a very strong German influence in all of them making them even more similar. This applies also to Gdansk.
The Poles have to be commended for the great efforts put into rebuilding the city of Gdansk, but this aspect is already well covered by Warsaw.
Still, I do see an inscription chance. If the inscription were focused on the Solidarnosc movement and the peaceful resistance to communism, I would be fully in favor of inscription. It's hard not to sense history when you stand at the gates of the shipyard with the Solidarnosc flag tagged onto it.
Getting There
Gdansk has an international airport that is served by multiple low cost carriers, e.g. from Hamburg. Getting from the airport to the city was a bit of a pain though due to heavy traffic. Gdansk is also well connected to the rest of Poland by train and bus.
Malbork is connected by train as is Torun. You probably also can travel along the coast to get to Stralsund in Germany. I ventured east via Elblag to Augustow.