Very quick one today...
-I'm loving the Advantage/Disadvantage, but for a slightly different reason than most people do.
For me there has always been a slight disconnect between role-playing and roll-playing especially in social encounters. On one hand, as a DM, I want the players to act out/role-play social encounters. If they are bluffing their way past a guard I want them to speak the words their character is saying. If they are trying to convince a sheriff to back their assault on a cult lair, I want to know how they are asking. On the other hand, sometimes a player just wants to roll his appropriate social skill.
Corollary to that is the disconnect between character and player. A player may not be good at improvising a speech during a social encounter. The player knows their limitations and thus compensates by loading up social skills specifically so they can do well in them with their character despite the fact they as a player is bad at it. If I, as a DM, require the player to act out the social encounter they will likely do poorly and thus likely gain a negative to their roll...which is exactly what the player is trying to avoid. The flip side of this is the player who puts nothing into their character's social skills because they know they can do well with social encounters simply because they, as a player, is good at role-playing.
Now I could ignore the role-playing aspect and only allow the die rolls to apply, but this is a role-playing game. I want to encourage role-play...not allow the dice to dictate outcomes with no input from the players. I could also ignore die rolls and base results purely on the role-playing aspect, but again we have the disconnect between player ability (player with poor social skills) and character ability (character with excellent social skills).
In the past, I've always done a hybrid version. Allow for role-playing which can add a negative or positive modifier to the die roll. But they always felt like half-measures. Either the bonus is too little to make the role-play "worth it" or too high so that the die roll practically doesn't matter. And, of course, there is always the issue of the subjectivity of it all; was the role-playing worth +2 or +5 or +10?
Which brings me back to 5E and Advantage/Disadvantage. In the sample adventure (which by the way is so much more than a "sample adventure") they simply state that during one of the social encounters ("can we prove ourselves to the monster that we are being nice to her") the person making the die roll gains an Advantage if they role-played the social interaction well. No muss, no fuss. Was the role-playing done well? If yes, gain an Advantage die. If not, resort to the standard die roll. There are no varying degrees of "should it be +2 or +5". Either it was a pass (good role-play) or fail (bad role-play) with the reward being a clear advantage to the die roll.
This makes social encounters so much easier to adjudicate.
And so many other situations. Did the player do an awesome job describing how she leaped onto the table, sliding down the bar and slamming into the face of the drunk mercenary feet first? Give an Advantage to the attack! Basically any time a player describes a character doing something cool, give an Advantage to the action. If the player is being dull and boring (or keeps repeating the same "cool" action), go with the simple "standard" die roll.
Advantage is a concrete and simple way to implement reward for good role-playing and narration.