I've had some spectacularly amazing
Without a doubt, this particular leaning has only been fed in recent years by the lion's share of my DM duties being one-player games. You don't really want instant-death scenarios in a one-player game in my opinion -- your player doesn't even have a buddy they can confer with before they trip that trap or poke that (undead) corpse in the shiny robes. There are more entertaining ways to cause a lone PC grief than just killing them.
Now, I'm also quite certain that the hardcore old-schoolers will gladly argue that point. Hey, if it works for you, right on! But I don't see it working for me and my players, which is also right on. And by disliking lethality I don't mean that I fudge the dice constantly or avoid challenging (and/or potentially lethal) encounters, either; I've dealt with gamers like that and it gets annoying. It's the instant kills that I prefer to not use.
Extreme PC stupidity, on the other hand, surely deserves pain and angst and yes death, if it comes to that. Without a doubt.
... I should write up a few poisons and post them here sometime.