I used to think that Sissel was one of the more bland and uninteresting forms of Cecilia, which as such is a name I really love and I also like many of its forms, including the Norwegian Silje. But lately Sissel has been growing on me and I think it actually sounds very refined and subtle. I definitely prefer Sissel to the Danish spelling Sidsel. Of course, my first association with the name is the singer Sissel Kyrkjebø, who I'm pretty sure must be the most famous Sissel in the world.