I was all set to say that dead ends were a vital part of the King's Quest series and any old school adventure game worth its salt, but now...
I definitely found the dead ends to be a part of the fun, and I have always been a save early, save often (in multiple slots) gamer, but I am starting to feel that they can be left out and the game can still feel like the originals. I think that dead ends were all about punishing players for their lack of adventurous spirit, or attention to detail, or what have you. I felt this was what drove me to try harder to explore every avenue (even when my 1st guess at a puzzle solution appeared to work, I often try some of my other thoughts to see if they get better/funnier results). But a player can be punished in different ways without having to be so frustrated, with lower score, less satisfying ending, shorter game, etc. If the player is told why he got the boring ending, he may want to go back to get the better one. Those who don't like to have to replay, don't have to.
I especially like one of the early suggestions of an easy difficulty level which warned you of possible dead end situations (warning you before you leave a room without a necessary item, for example), and a hard difficulty that lets you make any mistake you choose to.
I guess what I'm saying is that I believe that dead ends were valid, fun ways of making a game challenging, but if they make a new game too difficult for the average, modern gamer, then I am willing to give them up. In other words, if I get to play a brand new King's Quest game that might be simpler and funnier rather than satisfyingly challenging, then I am happy.