While a staple of American daytime soap operas I've personally never liked the concept. It smacks of laziness on the writers part or they try to be clever by having the audience think what they're watching is part of the story, when it isn't.
Though not quite on par with dream scenes I never liked the explanation scenes which Dallas would use to explain the previous seasons cliffhanger. Take the following;
You'll understand want I'm implying around the 2:48 mark. It was like the writers were going out of there way to explain to the idiot viewer what actually happened. It was unnecessary in my view and in this case weakened the character of Katherine Wentworth...or maybe that was the point of the whole exercise.