I'm gold (Group 2) exactly in the place to get hurt by full overhead bins on kid heavy flights. But having seen how it works on other airlines, and does not on UA, I can say that this will help speed up boarding. Plus I generally feel sorry for people with little kids who are forced to stand in the scrum line down the 7-narrow-7s UA flies, and then hold everyone else up as they try to get into their seats.

And as to these folks "grabbing your seat" come on. Were it to happen, the FAs will make them move.