So, uh...I'll probably be vilified for this, I dunno, but my first impression (from the song you kindly linked for me -- thank you) was that of a slightly uptempo Mazzy Star-type thing. The song was undeniably beautiful -- interesting choice of vocal lilt in the chorus's main line -- but am I a bad person for thinking "great intro, when do they get to the actual -- oh wait nevermind it's over already"?
Understand: I am not judging the almighty Sigur Ros. Yet. I still have a lot to listen to before I can form a solid opinion. This is just my first impression.