The location of their offices, Halden, might be a harsh place to stay for people used to bigger cities. Commuting from oslo could be an option but its expensive and takse a significant amount of time.
The company is fragmented in different departments, and even though everyone is really friendly, sometimes its hard to get things done.
Lastly, and this is something I've seen but not suffered, some parts of the company are more used to work in english than others (like internal talks at the office). This is by no means a problem or a bad thing from their side, but if you don't speak norwegian and you don't like to miss conversations going on, then speaking Norsk is quite handy.