Re: Do Bigsbys kill sustain or tone?
My experience followed that of TGB's. I had an Epi LP with a bigsby on it (stock).
Supposedly, the extra mass of the bigsby unit (it's a big piece of metal) should increase sustain. But in most cases, you'll need to upgrade/replace the bridge for it to be useable as far as tuning stability goes.
I remember from Earlwine's book that guitars originally designed for bigsby's had 'rocker' bridges. The bridges literally rocked forwards and backwards, as opposed to the strings sliding back and forth across the saddles. I have no idea where you'd find something like this, but there are newer options that probably work better anyways.
Another very sucessful option is the rolling saddle bridges like you find on a Gretsch. I believe schaller makes a version of this which replaces a standard TOM.
Lastly, you could just try and get some saddles and a nut cut from a very slippery material.