Save-or-dies... they're totally cool with me.
AS A PLAYER: If my character dies from some save-or-die effect, then that's just bad luck. I can't overstate enough that ***it is unhealthy and immature to be so attached to a particular character that you feel resentful or "cheated" if you lose them to a save-or-die effect* And I can't help but thinking that this is a motivation on the part of a lot of the players. If the DM overuses save-or-dies and keeps killing your characters, then that's a problem with having an obnoxious killer DM, not a problem with the system.
AS A DM: I understand that some DMs feel that save-or-dies may cause the potential destruction of their plot by killing some major NPC, etc., in a dramatic way. Well... **deal with it.** If a major NPC goes out to give a speech and gets in range of a Finger of Death and doesn't have some Death Ward magic in effect and fails their save, then you should have known that you risked it, and you should have a contingency plotline prepared. This is even stupider than complaining about the existence of Detect Lies and Know Alignment and Speak With Dead because you can't do that obviously-full-of-holes-and-not-meant-for-the-standard-D&D-setting murder mystery plot you were planning.
Only bad DMs drive the plot along on rails where it is "necessary" that the players accept the quest, or "necessary" that NPC X survives 'till the end. Not that a little bit of railroading isn't okay... but you have to be flexible. If the players kill your dumb end-of-the-dungeon dragon with a single failed spell, then you either let them enjoy their victory, or you have another monster waiting to take the dragon's place, so at least there's a fight scene.
D&D is about improvisation. It is about choices. It is about risk and randomness. You can never predict exactly whether your character is gonna die, you can never predict exactly whether your NPC is gonna die. You have to prepare for it, either as a DM or a player. If you don't, you are spoiling yourself.
SIDE NOTE: ....now, Save or Die effects that only work if the character is "blooded", that's a compromise I might be able to get behind...