First, let me preface this by saying that I haven't yet run EotE, nor do I expect to (though I'd love to). Second, for those unfamiliar with the term, let me offer this:
As GMs, we've all done it. In my old D6 campaign, I did it a lot. Your players' characters are in an encounter that they're supposed to walk through, and they're getting beaten to smithereens. Or they're at the big climactic encounter, and they're mopping the floor with the Big Bad Evil Guy. Many's the time I've thought, "thank goodness for this GM screen", so that I could tell a player that their opponent just rolled all 1s, when he really just rolled all 6s. The player loves to hear the news, and everyone's happy with the result, except the GM… because the GM knows that he faked it. And later, when the players regale each other with tales of that awesome victory they all shared, the GM nods, and smiles, and feels like a bit of a fraud… because he fudged the roll.
But here comes Advantage and Threat.
Player's character getting beaten up by the Jawa merchant he was supposed to get directions to the local cantina from? Advantage: Jawa merchant says, "I'd really rather be two blocks away at Rick's Cantina than over here whooping your butt". PC knocking the stuffing out of your unkillable bounty hunter nemesis? Threat: bounty hunter notices that the PC has the name 'Mary' tattooed on his arm and, next adventure, is going to kidnap 'Mary' to lure the PC into a later encounter in a place where he has the upper hand.
In other words, I love that this system provides a built-in way for GMs to steer the adventure back to where it ought to be, in a way that pure numbers just can't. Pure storytelling, no fakery, and… no fudge!
[EDIT: text colour is wonky, and I can't fix it! Highlight to read ]