This guy:
Fuck Mega Evo's.
To me, Scizor looks to be a major benefactor. If there is one Stat Scizor has always wished it had more of, it's: Special Defense
Afterall, Scizor has always been jealous of how TTar's bulk allowed it to effectively trap their mutual prey, and finally there is a way for it to enhance that beyond just throwing all its EV's in bulk. This should vastly improve Scizor's abilities as a trapper. Now with the whole range of potential between Adamant CB full attack all the way to Careful, bulky Assault Vest, fleety foes will have a lot more trouble figuring out where Scizor's bulk-power ratio lies. Careful Choice Band (more efficient stat wise) and Adamant Assault Vest (allows freedom of attack switching) just add more complexity and problems for Scizor's targets.
Moreover, Scizor is one of the few bulky offensive Pokemon who regularly uses 4 attacks-- Bullet Punch, U-Turn, Bug Bite, Pursuit, Superpower, Quick Attack, Aerial Ace... Scizor is not without good options for an Assault Vest set. It will probably be one of the item's most common users.