Matt,

I may be a voice of dissention here but I find the most influential factor on the sound is a WELL-SEATED saddle regardless of the material. I honestly feel that the vast majority of improvement heard lies in this simple fact. It's all about contact. Most of the time I've switched out saddles was because I needed a change in the string compensation. TUSQ, micarta, bone, ivory; I used them all, and have only noticed a change in tone through USDs (pickups).

Bridge pins: this one baffles me. It SHOULD be outside the acoustic chain - just like tuning machines. The only factor I see here is if the pins are substantial enough to add weight to the soundboard and affect the vibration characteristics of the top.

Nut: Again, this is a seating issue (to avoid buzzes) but just as important is a clean break angle for the string. I envision some improvement in sustain is possible but I think it's too far away from the soundboard to impart any noticeable change in tone.

In the end, if this is what you want to do and it'll make you feel better about your instrument, then go for it. But, if your looking for some noticeable improvement, you may be chasing ghosts. I mean, who's to say what's an improvement anyway? Maybe bone "colours" the sound... and somehow we've come to accept this as better because someone else says so?