A discussion over at rpg.net on this prompted me to write a comment which I then thought might be worth replicating here. Save or Die effects feel important to me in D&D, as a way of distinguishing certain encounters from the norm. What's a medusa without a save or die petrification gaze, other than another ugly monster to be hacked down? Here's my comment:
If I'm playing in a game where a medusa gazes at me and I don't turn to stone because the rules forbid it on grounds it would be a misuse of power...well, I sort of feel cheated. The whole point of SoD effects is that you should figure out how to overcome them by means other than "I have more petrification points than your gaze deals to me in damage," or whatever.
I did like how 4E handled this specific example, though (a series of consecutive saves), so I think one can find a middle ground between "missed your roll, now you're stoned" vs. "missed your roll, now your 10% on your way to maybe being possibly stoned."
On the other hand, I get the feeling that people who see SoD events as an abuse or misuse by the DM granted within the rules are either dealing with adversarial DMs (always bad) or missing the point of the game entirely. (this sounds like I'm endorsing the badwrongfun concept; what I realized after writing it was that I was asserting that "rulings, not rules" is my preferred default stance; don't think fixing the rules stops a bad DM from making trouble, I say, so leave the rules as flexible as possible and provide as much "how to be a good DM" subtext as possible).
All I want is a version of the game that reflects consequences intelligently and in a way that doesn't suspend disbelief. If my PC drinks hemlock and doesn't have a strong chance of dying as a result, I will be disappointed. If my PC locks gazes with a medusa and suffers no ill effects....I will feel cheated. Just my 2 cents. I will be happy with any system in which I feel that the point of SoD effects is retained, even if the mechanical application lets players feel like the results are "fair," I suppose so long as doing so doesn't kill the point of such effects in the first place.
If you have, say, a medusa with a SoD pertification gaze that works like it says on the tin, then the players should reasonably expect to approach a medusa differently from any other monster and deal with her carefully, at a distance. If the medusa's gaze is turned into a "save or start accumulating penalties or moderate damage with an end result of petrification" it changes the fundamental approach to a medusa from a tactical, measured consideration to a zerg rush from the players. This effectively removes a tactically interesting encounter from the game, I feel, and replaces it with an entirely different approach that sort of defeats the whole concept of the monster in the first place.