As for other dungeons. Usually they have specific mechanic that makes walkthrough easy or difficult. "Tentacles and beach" dungeon became hard because party suddenly got "stun parasite". This added random into the boss fight.
"Petplay dungeon" suddenly has confusing maze. Mostly because sometimes you can't return to QB, and get no idea of where to go. It's unfair and sometimes frustrating, but adds some challenge and interest.
To be honest, I got pretty serious into Ero Witches because of challenging and confusing dungeons, and familiar setting. And forgot that it's just parody of "mahou shoujo deconstruction". Due to this I was surprised by talks in "addiction dungeon" and the ending.
I found few bugs. One in "petplay dungeon" when you go downstairs.
Another are glitches in final boss fights. Boss puts straitjackets on girls, but their arms are somehow free.
After playing Ero Dungeons I figured out that it's first game and probe. It's interesting and addicting (sorry for pun), but level-design is frustrating sometimes. So I'm pretty interested and looking forward at Ero Dungeons.