No rest for the wicked...
Reynard said:
Between the end of vancian casting, constant self healing, the removal of "unfun" save-or-die/suck effects, the treatment of traps as terrain and the dungeon as an arena/gauntlet, I somehow doubt gritty dungeon survival is even considered as a playstyle appropriate to 4E.
It appears to me as if traps in 4E are not terrain, but more like a monster, but I might be wrong on that (or it varies depending on the kind of trap.)
The old-style "attrition-based" gritty dungeon survival may be done. But so far, most 4E playtest reports I read indicate that the individual fights are still pretty tough, with characters dropping right and left*. Admittedly, they are standing again after a few rounds, but that's only because in the end, someone survived to patch them up, and they weren't dropped dead, just unconcious...
If players know to get through a dungeon they will have to face mutliple of such encounters, they feel challenged. They feel like their very survival is threatened, because in each individual encounter, one of them could have died. Or all of them. The enemies have to get lucky only in one encounter - the PCs in every single one of them.
In the attrition-based style, players enjoy a little more safety - in the beginning - , because they know that it will take some time until their resources are mostly down. They know that it's unlikely (assuming good tactics and teamplay and a fair DM) that an individual encounter will cost them all their resources (or their life). Only at the end of the adventuring day they will face the real challenge, because their remaining resources are challenged, and only at this point they will figure out whether they were good enough in the previous encounters to have enough for this one.
The main difference will be pre 4E, people used to rest inside dungeons if there was any chance to make that possible. In 4E, this will no longer be neccessary, and the PCs will run for their life to get the fastest out of the dungeon then possible. (Assuming it's such a gritty and nasty one).
From a versimilitude point of view, I think I prefer the latter "strategy". Resting is reserved for wilderness travel or visits in settlements.
*) if you find any exaggerations in this post, you may keep them. 