It is. You've got the feeling that most of the time, the roads either go up or down, not to forget the zillions of often rather dark and sometimes very long tunnels. The day I took the pictures linked in my post, I drove about 390 kilometres from Rosendal to Kristiansand and it took me about 8 hours. (Though I've got to add that I stopped at least 10 times - possibly more - to take pictures of the fascinating landscape, which also took some time, always trying different camera settings.)
Here are two pics from the way over the Haukelifjell (about 1000 metres above sea level), taken at a trip four years ago when the weather was absolutely perfect (and not as rainy as this time):
