If you don't "get" Sigur Rós' music you might want to steer clear of this one, the rating I gave it reflects this, it would be much lower if you don't care for their style. There are some great, gritty visuals and the music is well played but it is very impressionistic, to the point of being fragmentary. I would recommend there film Heima for a better look at the band, with many of the same songs.
This is the 'film noir' of rock music documentaries.
This is the 'film noir' of rock music documentaries.