Don't forget "Hoppipolla", "Sæglópur", "Untitled 1", "Untitled 2"... really, the band seems fond of this trope.
True Art Is Angsty: Their angsty songs (to be precise angsty melody since nobody understands the lyrics) from the earlier albums like Viðrar vel til loftárása, Untitled #1, and Sæglópur were received better by fans and critics alike compared to their Lighter and Softer approach for their last album Með suð í eyrum við spilum endalaust.
On the other hand, by far their most popular song is Hoppipolla, which is definitely Lighter and Softer.
Also, ( ), being the moodiest of their albums is often considered one of their weaker works.