I think the use of the soft pedal is directly related to the musician using it. Many of the concert players I know and have tuned for "ride" it in a similar technique to their use of the sustain pedal. As a precaution, I try to always check and voice the hammers to it at various measurements of depression so as to not have an embarrassing zinger stand out more on half pedal than on quarter or whole. Its remarkable how one tiny hard spot on a hammer can create those metalic nightmares during a concert when all seemed fine with the soft pedal fully on or off. I agree that it should be regulated for the correct shift and then the hammers voiced accordingly.
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