I like being in contact with the flies (I normally fish 2) at all times. My indiactor is bi-colored leader material. I keep an eye on that during the drift. Helps determine if the flies are getting down too. If its moving as fast as the surface current I know my flies arent penetrating. If its moving slower than the surface current I know Im in the zone.
I do use indicators occasionally, when its windy or if I am fishing at a distance. Ive played with the yarn indicators, those were fun. What I got addicted to is fishing dry dropper. Epecially around August/September.