Just to be clear, circles are absloutly not the best choice when used with artificials. I don't use them much in the NW even for halibut since basicly all my fishing in the salt is done with artificials and my preferance to troll downriggers most of the time.
How ever, in Hawaii and Florida or anywhere I'm using live or dead bait, I love circles. I grew up with them in Hawaii and they're common-place among virtually all bait fisherman there. That's why I experimented with them back when I mooched alot. The circle near the tail of a cut-plug just doesn't get those short strikers, but anything large and/or hungry enough to take it whole is gonna get that circle in the front.
Rule in my boat when releasing salmon, is it doesn't come in the boat no matter what, even when trying to up-size a coastal King. (1 fish limit last year) If it touches the net, it goes in the box. I'd imagine removing a circle boat side is difficult since they really don't get off them on their own once their hooked on 'em anyway.
The only place I'd consider using them in WA is when flyling live 'choves to albacore, besides using them as the top hook in a tandem mooching rig. The design of the circle definately offsets the disadvantage of barbless octopus hooks when that Chinook gets rockin and rollin