Surströmming is actually quite tasty. It just smells really strong. You never eat it indoors. There are other ways to pickle herring that are less time consuming and demanding, though.
Lutefisk is kind of a misunderstood dish. Like many other old traditional 'delicacies', we've forgotten why it's made that way. In this case, it was a question of preserving the fish in lye to make it last longer. Prior to cooking you're supposed to water it out. Many modern people seem to have forgotten that. They only water it out for a little bit, and then they think it's supposed to be all jelly-like. It isn't. You treat it properly and it tastes like, well, cod. Which it is. Of course, in this day and age you might as well just cook cod.