I spent some time on a crowded (fish & fishermen) river this morning and gave circle hooks a try. I tied a couple of my most successful patterns on size 8 hooks, put on a type 3 versi-tip and proceeded to lay casts almost 90 degrees to the travel lane. I consider myself a decent fisherman and feel confident that I can usually tell the difference between a snag and take. Circle hooks proved I wasn't nearly as good as I thought. Each cast I would feel multiple bumps and taps, often mistaking the tap, tap, tap for a take, but when I'd tighten up there was rarely anyone home. Every ten to fifteen casts or so, I'd feel the line go tight and all I need to do was start reeling, the fish had hooked itself. Meanwhile anglers around me were pulling in foul hooked and flossed fish every other cast. In the end it allowed me to feel just how many times I had the potential to foul hook and how few times a fish actually took my presentation. I would challenge other anglers to take their favourite lure or fly and try it with a circle hook and see how good it really is!
I should add that type 3 is not my line of choice, but it is on the light end of what I see many fly guys tossing so I felt it was good for the test. Ultimately, thanks to a report from Milo I had the most success with a floating line and a short leader slowly retrieved well above the schools. This resulted in great takes, fresher fish and more fish than the type 3. In fact I'm convinced the type 3 only spooked fish through the swing and ended with a hookup on the dangle because of sheer volume of fish pushing upstream (there is always one Darwinian fish in the mix).