Name says it all. Mini Bosses are cool! There should be a mini boss in each dungeon where you acquire the dungeon's item.
Hmm. That's not a bad idea. For the large dungeons anyway. I'm not sure I could do a full boss battle, since that's about a week's worth of work, but I might be able to add unique enemies that you get trapped in the room with. I'll consider it when I start adding more enemy types!