Just a short anecdote from my game this evening, which I loved.
The characters had been split up: two were in the mall while the other two were in full on Breakfast Club mode serving out a Saturday detention.
I started off playing the scene with the mallrats, which involved the Fae attempting to gaze into the abyss by looking into a shop mirror, utterly fluffing her roll and walking out with a new minidress (but I digress). While I was playing out this scene however, the detention kids were secretly passing notes to each other. This exchange of notes ended up quite extensive (and hilarious, at least to us).
Overall, it was totally unexpected, showed great player initiative and worked brilliantly. And it sped up the whole narrative as we were effectively playing two scenes simultaneously.
It worked for me anyway!