I've found that bitterness, served on a felt pillow, can actually be pleasant. Combined with other foul notes however, and it gets named as a primary suspect at the crime scene.

Could just be marketing spin, but I've gotten the impression that the fines produced by the NZ was part of its magic, and I associate fines with increased bitterness.

This works for flat-burr grinders, so maybe it will work for conical grinders (NZ) too: try slow-feeding beans into the grinder., such that is takes at least twice as long to finish. My theory is that reduces overcrowding and grind-on-grind crushing, making the output more unimodal with fewer fines. On my flat-burr grinder I've had to significantly reduce my grind setting to compensate.