Scenario 15 is insane, but I managed to complete all of them except 15-1.  I feel like I'm just missing some step, because even when I managed to get the companions to the exit, I was unable to get myself out.  Anyone have any pointers for this level?

Sorry for taking so long.  15-1 isn't too bad.  Just put the adult and the kid on the rightmost pulley.  Then go to the top left, hit the button, and immediately run to the right until you're at the bottom again (a crate and the pulley should just miss you).  Then go back to the top right.  Get the kid to take the rope, then give it to the adult.  The kid should crawl into the space just above the exit, while the adult climbs down and crawls onto the switch.  Then you can jump onto the boxes on the pulley and into the exit, while the adult can climb up and make it in herself.

Thanks!  I was missing the step of rushing under the falling pulley, which of course was leaving me stranded on the left side.

With that out of the way, I think I'll finally attack the last levels of the game to try to join your 180/180 club.  It's quite intimidating though that only 5 people have completed levels 19 and 21 (according to the leaderboards).

Well, if it boosts your spirits, I still think Scenario 15 was the hardest. :)  The second hardest was probably the timed one (20 or 21?).