I am referring to loops for joining lines to lines, and lines to butt sections. I've been meeting more and more folks who prefer the loop knot of which you speak (terminal to fly) to enhance the action.
Basically, you tie an overhand knot into the tippet as a stopper, then tie a clinch knot above the stopper knot. (Brian - care to clarify for grego?)
I tend to try to design flies to be active in the water as opposed to changing the terminal knot. This all depends on the fly, in other words the best knot in one case is different than in others. For instance, I prefer to use a double turle for upturned loop eyes on steelhead / salmon flies. This also suits the riffle hitch for skating the same fly where the loop knot would not. But that's another story and I guess I am not staying on topic...
As far as stripers are concerned, I think the heavy tippets and motion in the water (ie: surf) make loop knots a good idea. But you don't need a loop knot for a felt crab. Sand eel patterns don't typically move in the front section, but you want a lot of motion in the second half of the body. I don't think a loop will help for many of my solid forward body sand eel patterns. For a popper, I probably prefer a nice solid tie to a stiff tippet. Juvies, on the other hand are probably a good fly for loop knots although I feel confident that the marabou abdomen I tie in makes the hackle tips dance in the foil regardless of the terminal knot.
I'll try them out this season and see if it makes a believer out of me. We should have a lessons learned season-ending discussion for the record as well!