aside from when it is a twisted up mess, as noted above, i think the string is a work of genius. most of my time is in the astar and their airspeed indication is somewhat lacking at low speeds, so the string is ever useful when working at high density altitudes. the 407 has a pretty good pitot-static system, but i find the string much easier to use when on short final to cliff side pads.
just me, tho'
regards,
fp