EmbraCraig
Explorer
When I DM, I roll almost exclusively in the open, keeping very few rolls secret (usually my rolls for "does something happen", when the players don't know exactly what I'm rolling for anyway). Let the dice fall as they do, sometimes I've hit a player with 2 or 3 crits in an encounter, one time a group of archers rolled 1s for about 80% of their shots during a fight... these things happen.
As a player, some of the GMs use a screen, some don't... I don't have a problem with either, as I've generally trusted my GMs. The only time it's bothered me either way is with a GM who rolled behind a screen, but was really bad at letting the dice decide things - he sometimes made it very obvious that he was re-rolling the result because he didn't like it (and sometimes did it 2-3-4 times on the same roll...). Not that he was biased for or against the players, just he wanted to make sure a certain thing happened - I never got why he rolled the dice in the first place in those circumstances.
As a player, some of the GMs use a screen, some don't... I don't have a problem with either, as I've generally trusted my GMs. The only time it's bothered me either way is with a GM who rolled behind a screen, but was really bad at letting the dice decide things - he sometimes made it very obvious that he was re-rolling the result because he didn't like it (and sometimes did it 2-3-4 times on the same roll...). Not that he was biased for or against the players, just he wanted to make sure a certain thing happened - I never got why he rolled the dice in the first place in those circumstances.