As a player, I prefer them be out in the open. I never worry about being cheated by a DM (I'm fine with having it stuck to me) but, and this goes with what you said, I don't like to think punches are being pulled for me.
This.
As a player, I want the rolls out in the open so that my PC takes his lumps and has to come up with cool ways to overcome the dice gods. And it reallly sucks when a DM purposely goes out of his way to protect or harm a PC.
DMs who hide the rolls take that level of fun out of my game.
I was nervous when I first switched, thinking "But what if the fight is too hard?" but I've come to trust my own ability to build appropriate challenges that won't TPK the group.
This.
Most encounters should be challenging, but not life threatening. But if there is no chance of death (or at least the potential heavy use of resources) even in an easy encounter, why bother to play the game?
It's actually eye-opening in a way to see that so many people have to "roll in the open" so that their players don't accuse them of cheating. I'm glad our group doesn't require a similarly level of proof of integrity.
It has nothing to do with proof of integrity. It has to do with integrity.
It's a matter of human nature. The best people in the world are going to be tempted to fudge if the dice are hidden either to help or hinder the PCs, depending on the current situation and their whims.
I think that DMs who need to hide the dice need to control the situation.
Hiding vs. not hiding is all about control from a DM's perspective.
And like I said, it has to do with fun from a player's perspective. As a player, I want to work my tail off to overcome the Dice Gods, not to overcome the whims of a DM.
I don't want my DM to write the monster's AC down on the white board so that I know what it takes to hit ... and I don't want to know whether the monster just hit my tank fighter twice because it rolled an 18 and a 19, or because it hits me on a 6 and I'm in real trouble.
Trust me. I'm going to know the approximate AC of most of the foes in a matter of 2 or 3 rounds anyway.
And a good DM should be describing a hit with a 6 (if he needs to hide his rolls) as:
"The Ogre backhands you with contempt, hardly even trying but connecting solidly nonetheless."
I should know as a player that this foe is just toying with me by the way the NPC fights.