I've completed the details for the first "level" of my sprawling 450 room mega dungeon. It's more of an "area" of the dungeon than a "level" in the traditional sense. Everything has been randomly generated - although I have selected about 3-5 rooms for specific encounters etc. All tolled this works out to about 88 rooms. I created (what seems like) innumerable random charts in excel to determine room contents and details, above and beyond monsters and treasure. I prefer customized charts that reflect the specific nature of each dungeon I create. For example, I've used a variation of the Labyrinth Lord Stocking table, as I wanted a higher percentage of empty rooms.
I've pulled out all the tricks to highlight player choice - I can't speak in too much detail as my players read this :P
At this point, it's on to the narration while I also peck away at the next set of tables for Level/Area 2.