There's been a lot of discussion of this issue on the flatpick list (interminable, actually). I replaced the ebony pins on my Taylor with bone ones and did hear a rather noticeable difference in sustain and punch. Both bone and FWI pins will tend to sharpen a guitar's sound, but not always in a good manner. I suspect rosewood boxes might benefit more than mahogany or maple from such a change, being made a bit less "muddy". I also think that dreads are better candidates than smaller bodied guitars. My 0-18 got rather harsh sounding with the bone pins when I tried them out. YMMV of course.
Sandy