"Vanilla" DnD to me is as follows: the DM makes up a setting (dungeon map, encounter key, or more sophisticated equivalents), players explore the scenario, DM adjucates results based on a combination of versimiltude (what "makes sense") and random dice rolls. Death is the same thing as taking 5 points of damage, it's one of the possible outcomes of following the rules. This is the impression that someone who reads the PHB would have if they never read EnWorld or played with Storytellers.
PC Death is not fun. But neither is losing at soccer. Or a more appropriate analogy - neither is failing to meet a personal goal. Yet a personal goal that can always be reached is not worth achieving IMO. Not being able to die is not fun for some people (like me), yet dying is not what I'd call "fun" either. It would be very complicated to try to sort out the meaning of all of this - hopefully the soccer analogy explains it. An "adventure" where my PC has a chance of dying is exciting.
And that brings me to my concern about PC death in other people's games, which is what happens when Storytellers aren't honest about the chance of death. I've played in such a game. There's an expectation when you read the PHB that I've covered in paragraph 1. Storytellers can take advantage of the dramatic tension created by the illusion of random chance, player choice, etc. The first time the DM fudges some dice behind the screen and the PC survives, it's probably pretty exciting. However, IME players have a running stats meter in their heads and over time, fudging becomes pretty clear for what it is. When I've reached that point as a player, it's been very disappointing. And no, just because the DM runs the game doesn't mean he can be dishonest about what kind of game is being run. As people playing a game, we sit down at the table as equals.
The challenge/problem for Storytellers is that the vanilla version of DnD doesn't support their style - and neither do the default expectations. I expect the same thing from a Storyteller DM as I do from someone (like me) who wants to use a certain set of house rules - because the situation IMO is the same. It's not a matter of one way being "better" than the other (I happen to think my houserules are pretty cool). It's just a consequence of the PHB being the default reference point.
If a particular Storytelling group has been playing together long enough to figure all this out, then that's cool. If the situation is explained upfront (DM: "I'll decide who dies, don't worry about the rules") then that's cool. But what I've experienced, and what I read between the lines on EnWorld often, is that the DM is not always honest about how he's running things. He often seems to want the best of both worlds, at the cost of honesty between people at the game.
So ultimately, IMNSHO, PC Death is not as important to the game as being honest with your players about how you're going to run it.