A vertical dungeon. Has anyone ever tried that?

[Kaptin Keen]

Having a map doesn't affect whether players can have creative ideas nor whether someone can improvise and react to players decisions.

Yes it does. If you map it out, you're locked. It's only there if it's there. Say, the teleportation chamber, or the pantry, or room full of leather eggs. I can describe all of those if I want - but if the players come up with something, 'say, if he's a necromancer, does he have a giant pile of discarded bodyparts somewhere - like a bit box in a workshop?' I can only pop one in there if there isn't a map.

It does mean that there is a fair and objective way to determine the results of certain actions and no ambiguity about where things are and how long it takes to get there.

What you're looking for is an equation, a problem>solution kinda thing. What I'm looking for is interaction. Also, it seems you have trust issues: I'm fair and objective, and I have my players ambitions in mind much more precisely than any map ever could.