I bought some a while back for saltwater. They were on sale and I might only use them once every year or so, so figured I'd have at it. Have not used them yet, but I like the concept. Especially when dealing with toothy fish, to have the hook imbed in the side of the mouth is a plus to keep the teeth away from the leader. If I go for pike, musky, or walleye I might tie them on circles too... don't see any disadvantages to it.
Circles work great with bait and are a staple in saltwater (sometimes required by law). How exactly this form of hook manages to catch fish in the corner of the jaw remains something of a mystery. Circles are hard to find in the tiny sizes needed for so much trout fishing and they don't exist (at least I haven't seen 'em) with long shanks suitable for streamers. I posted a thread about the "Moffit System" on this site some months ago and will be experimenting with circles this year. I also tied some fairly large nymphs and egg flies on the smallest circle hooks I could find at Bass Pro and, once I get some time using them, I'll post a review here.
I think tying my version of the san juan worm would work just fine on a circle hook and the fact that mainly i use them on wild brookie streams and the fact that they have pretty non-destructive hooking qualities (corner of the mouth) they would be just fine........any bites?