Treating it as the same language would be a stretch.

As a Swede, especially spoken Danish is completely unitelligible.

Having worked with Norwegians the last few years, I have learned to understand spoken Norwegian most of the time. There is however a lot of variation i dialects, making some of them easy to umderstand, while others are almost as bad as Danes.

In adition to dialects, there are enough unique words and idioms in each language to make especially written norwegian cryptic.

There are also a lot of gotchas where the same words have different meaning. A fun example is the expression "rar tös" meaning "sweet little girl" in Swedish, but "weird slut" in Norwegian.