Faolyn
(she/her)
While I haven't played 4e or, indeed, read any of the books, I would imagine that something like those sewers should be treated as a single challenge if they existed only as an obstacle and there wouldn't be any fun to be had actually going through every intersection. If there are no clues to be found, treasures to be claimed, NPCs to be dealt with, monsters to be fought--if the only point of those sewers is to get through them (or, perhaps, to get through them in X amount of time or less), then I can't imagine there would be much fun roleplaying finding your way through it.The rather key part that seems to be incompatible to me is the degree of granularity (particularly in combat) of resolution and in the mechanics which support that; present in D&D (more or less) but not present in some of these other systems as described here and elsewhere.
I don't like the idea of 4e-like skill challenges for the same reason: they allow too much granularity and too many details to be skipped over.
My usual example here is a maze of sewers under a city, through which the PCs are trying to find their way from A to B. 4e would reduce this to, it seems, a single skill challenge, and other games would reduce it to a similar single-roll resolution; where I want them to have to make a choice at every intersection and, preferably, make even a vague map.
Why?
Because every choice point allows them an opportunity to do something different, or decide to take a side trek, or go a different way, or turn around and say "bugger it, we're going above ground for this!".
Yes this takes longer at the table. I don't care.
Sure, the PCs may decide to go a different way... but is it really fun to get so annoyed in-character that you want to turn around and go a different way?