since no one has answered i'll tell ya what i know and it ain't much.
i travel lots of oklahoma, farm , feed stores and coop's
i see them at lots of places and i,ve nevered used one, but i know one guy around rocky/gotebo and another down in chattanooga that uses them on summer stockers and thay seem to be pleased.
as you stated you don't have to gather the herd to treat one animal, less stress and etc.
my personal opinion and for my needs i don't like it.
i handle mine enough so running one through the chute in not a problem.
i would be concerned that the full dosage was administered, the shot placement would not be where it needs to be, bruising and blemishing and etc.
i feel like you should examine the animal up close before making a diagnosis, instead of drive by shooting.
but thats just me