I cast off my second Lopi sweater this weekend, and promptly went snowboarding in it. It was really warm!
I used the Árni pattern, but knit it top-down, I made the sleeves separately however, for portability, and then kitchnered them in place. I was really happy with the easy pattern, and it fits great! I've been on quite a sweater kick, and I'm sooo tempted to make another Lopi, particularly since my LYS is carrying the Icelandic wool now.