These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Magnum Opus: Many, if not most fans say obZen. Koloss, with its organic feel and dense, epic sound, is a close second. Chaosphere is in third, as it is the album that solidified the band's current sound.
The lyrics to a lot of their songs are also terrifying, particularly the lyrics to "In Death - Is Death" and "New Millennium Cyanide Christ."
Seinfeld Is Unfunny - Metal blog Metal Sucks is already speculating that Koloss, in the post-djent metal scene will suffer from this. It did suffer from some backlash but was generally praised by both fans and critics.
They Changed It, Now It Sucks: Some older fans didn't really like the post-Chaosphere releases, as they felt that the band lost much of their musical aggression with their greater focus on slower, Pantera-esque tracks. Nothing and Catch Thirtythree, in particular, get hit by this sentiment the most.