Although I miss the vertical aspect, I wouldn't want it with the current OB dungeon mapper. DF dungeons was too confusing for me to fully enjoy, even with it's 3D'ish mapper. But I'm confused about the dismay about Oblivions dungeons. I think they rock. There are some cool, big, and highly unique ones. But the general purpose dungeons look exactly what I would fantasize them to be. Sewers looks like sewers, with water canols. Caves look like caves, just tunnels. Mines look like mines, with some reinforced walls. Forts look like prison forts, some even with cells. Ayleid ruins look like, well, how they should look like
Sure, there is no castle within a dungeon, like that epic dungeon in DF. There could be a little more puzzle work and more traps. Maybe some tonal changes to colors, but don't get wild about it either.
My only request would be to make dark dungeons *dark*. Use of light should reveal you as a (possible) threat (sneak pretty much ignored). But some should also be well prelit with candles, torches, crystals, and opening to the outside world to let light in during daylight. Oblivion dungeons were far too bright when there were no lightsources around.