I've been rather quiet on my megadungeon project of late, and that is because I've been dissatisfied with my efforts up to this point. The problem is that I was bored with the maps I was drawing. They just didn't capture my imagination, they didn't seem like the sorts of dungeons I'd want to necessarily play in. I think I was drawing a dungeon more like an office building, and while an office building might be efficient, it tends to be boring. I need more chaos in my dungeon, more weird! The maps I'm most happy with are the ones that aren't actually a part of the main dungeon!!
I've also got everything pretty much flat. There isn't any reason why any level of the dungeon needs to be all the same depth, as my levels should be more relative, which can give a greater ability to make interesting areas to play in. While much of the dungeon will be composed of rectangular rooms, I'd like there to be some interesting features for characters to play on/around/with. Stairs, balconies, rafters, ropes, chandeliers, etc.
I have a room that I'm really looking forward to drawing up that will take advantage of a number of these features. Expect to see it shortly!