In my Vats of Mazarin game, I've been beginning to discover that character level seems to progress much faster than dungeon level. Now, the first level of my megadungeon is quite large, about 80 rooms, but even after exploring only 50 of them (although they've found all but two areas of interest), the party has reached 2nd and/or 3rd level. Maybe it's because the party is quite small and thus splits the experience only a few ways, but they seem to be stocking up on hirelings and henchmen. There have even been five character deaths and everyone is still progressing so quickly compared to the level of the dungeon they are on.
Part of the problem, is that I've made the dungeon too interesting. That might be the wrong word, but seem like the players are apprehensive about missing anything - they want to explore everything that there is to be explored and gleam every bit of knowledge out of it they can find.
I'm starting to appreciate more the Arnesoian three level system: Flunky, Hero, and Superhero. Different parts of the dungeon could geared towards the three character levels with each level of the dungeon being more of a thematic change that an increase in difficulty.
On a completely different note, I've begun to think more about X-Plorers. The Fight On! Random Tables book has some really great gonzo science-fiction related tables within and I'm just itching to get some use out of them. I have some definite issues with the game, rules wise, but who knows, it might play great even if I don't really get it on paper. I want to get some experience with it under my belt before I start house-ruling the crap out of it.