I've only just started playing dead-is-dead, and I have to say it is remarkably fun. Today, I almost died from a troll attack, and rather than thinkign "Oh, if i die, I'll just reload", I was actually concerned as more of my blood splattered around the place.
As for when to reload, I think it comes down to how hardcoe you want to play.
For instance, I quicksave every time I go inside and outside of a building. That way, if the game crashes during a load animation (it happens), I can reload.
As for the situations you listed.....well, I've never heard of the Ring of Silence, but if you die from eating a posioned apple.....that's just a stupid mistake. Look at the tooltip in the bottom corner before you chow down on something.
And as for a quest death....well, that's up to you. If I were to die from getting attacked by Mankar Camoran, well, I'd say -- "You should have levelled up more".
I don't think there is any situation where you would die and not be able to think "I could have done XYZ to stop that".
So, I would say, unless the game crashes obviously, or you encounter some kind of bizarre bug where a mudcrab manages to kill you instantly, dead is dead. That's as simple as it gets.