We've touched on themes. We are still talking about which systems work best with the megadungeon format (surprisingly it's a very varied grouping of systems).
What I'd like to talk about now is "what levels work best for a megadungeon?"
Does the format work best with lower levels, middling levels, high levels?
Does it work equally well across the board, or do you need to make certain adjustments at one extreme or the other?
Does it work better or worse with a system that is level-less (generally sill based), such as GURPS, RQ/Legend, Savage Worlds, etc?
Is it feasible to have one megadungeon go from level 1 to 20, or should there be a grouping of smaller megadungeons that are linked thematically / by story / regionally / etc and are broken down by level ranges?
Can a megadungeon actually be a campaign setting? Can it be a sandbox styled setting?
You've all given me much to think about over the last few days. I suspect you've given each other a lot to think about to. I'd like to hear your thoughts on the matter.