The combination of Vladimir the dwarf's death due to poison and my recent dissatisfaction with S&W's saving throw mechanic has gotten me to think a bit more about "save or die" effects specifically and saving throws generally. My default presumption nowadays is that "the dice don't lie," which is my way of saying that, most of the time, random rolls result in a much more interesting "story" than any I could plan beforehand. That is, if "story" is what happens after the fact, once the players acquire some distance on events and retell them later, then a random element can't possibly "destroy" it. Those random elements are just additional events that the players can describe after the fact, imputing to them meaning and relevance that they didn't, at the time, possess.
Consequently, I have no problem with killing a character based on a single random dice roll. What's interesting, though, is that a saving throw vs. some death-dealing effect is rarely the only thing a player can do to save his character. In my experience, to be in the position of having to make a Hail Mary roll like that, the player already has to have made one or more bad decisions -- or at least that's how it ought to be. In the aforementioned case of Vladimir, the players all knew from previous experience that the dungeon was filled with molds and fungi that released poisonous spores if disturbed. And yet, when finding an entire room covered in the stuff, a room that included mold-encrusted human skeletons to boot, Vladimir nevertheless ventured forth, torch in hand, to try and rid the room of its fungal infestation.
I take the term "saving throw" literally. It's a player's last chance to save his character after having made a poor decision. Without it, Vladimir would simply have died when he set the torch to the fungi. Instead, he got a chance not to suffer for the mistake he made. To my way of thinking, that's fair and even generous -- one might even say "heroic." After all, if I were to enter a room filled with poison gas, I'd probably die almost instantly. But then I'm not a resilient D&D character, never mind a dwarf counting on his race's resistance to poison to save him in the event things turned ugly. Normal guys like me don't tend to get saving throws when we do stupid and dangerous things, but adventurers do; that's what makes the adventurers.
I readily grant that the way I handle "save or die" moments may not be the norm and probably never was. As I interpret the rules, though, a saving throw is intended as a check against player stupidity, a final "objective" opportunity for a player character to survive even though, by all rights, he shouldn't. It's not unlike a 1st-level character who decides to take on an ogre (a 4+1 HD creature). Chances are the character is going to be slaughtered, but the dice might roll in such a way as to turn this foolhardy attack into a glorious victory against the odds rather than into the ignominious defeat it deserves to be.
I'm lucky in that my Dwimmermount players have all very nicely internalized the old school way of playing: they're cautious, methodical, even a little underhanded in the way they approach most problems. Consequently, they've avoided lots of situations where they might well have died, or at least where they'd have had to make saving throws to avoid doing so. That's why, so far, there's only been one PC death. Frankly, I'm rather proud of them. I certainly take pleasure in watching them puzzle things out and "beat" me at my own game. I don't want to kill their characters, but I will if they do something that, by either the rules or the logic of the game world, ought to kill them.
They all know this and accept it and that probably explains why they make such a concerted effort to avoid making foolish mistakes -- just as it should be.