People occasionally say they dislike "save or die" mechanics. The latest example is either Mike Mearls or Monte Cook, in a recent WotC article; I haven't read it, so I'm just going by blogger buzz that it is, in fact, the case. The usual reason given is: a high-level character can be suddenly laid low by a single rattlesnake bite, exactly as if the character were a measly 1st level flunky. It's unheroic. (I've even seen the same feelings expressed about "static armor classes" that don't improve with character level.)
I like save or die for exactly that reason. I could call "realism!" but it's really a matter of maintaining a minimum threat level. With save or die rules as written, absolutely anyone can die at any time. You can't become blasé about adventuring just because you've amassed a bunch of hit poiuts; you have to take precautions and play wisely.
Some people would prefer to ignore low-level threats after they've proved themselves worthy, so that they can just focus on "boss" monsters. I suppose they can play however they want, as long as they don't take up a contradictory position, like complaining about 10th level fighters walking away from 100-foot falls.