I saw a Danish tv programme subtitled in Norwegian. There are differences, but I have observed people from the Denmark.Sweden/Norway speaking together and they tell me they each talk their own language and don't have to adapt so that the other person can understand them. On the other hand, some people in Norway even call two main Norwegian dialects two "languages".
the other Scandinavian language besides Finnish that's very different is Sami (Lapp). How well do Sami in the different regions intercommunicate?