Save or Dies make things a lottery. Don't want them back.
As for elements that can't be replaced by simple "save or suck" or "you get better" mechanics, 4e has the poison/disease track - which is an elegant and flexible replacement for the clunky mechanics of level drain (for one thing it means that your condition in some cases can get worse.) It's not often used in my experience (for that matter nor was level drain), but works well for things like Lycanthropy, infection by certain parasites, and poisons.
FWIW, I really like the 4E disease system, too., and have incorporated it into my PF game -- including using it for magical curses and insanity. But it doesn't *replace* save or die or energy drain.
Here's an important thing, IMO: it is damn near impossible to produce actual fear in a player at the game table, and equally difficult to get a player to make his character act as if terrified of some monster. However, give that monster a save or die or level draining touch/gaze/breath/whatever, and suddenly in game you have terrified PCs run by terrified players. Even Conan got "scared" when faced with the truly weird monstrosities of the ages buried beneath the earth. Whether it was the original design intent of save or die and level drain, the effect was just this.
That's why it is worthwhile and why I think you'd find that in general DMs are more positive about it and players are more negative (those there's exceptions both directions, of course). More to the point, they shouldn't be removed. Alternatives should be offered and advice should be given, but not taking them out of the game.