i've owned warwicks with both versions of the just-a-nut... brass and graphite/graptech or whatever.
I'm not really a fan. I believe it's very rare you need to adjust it, even if changing string gauge, especially if the slots are cut right (which they always are on a Sadowsky), so then all you're left with is a lack of consistent coupling across strings at the headstock. yah, ok, maybe a subtle difference in the practical world, but nevertheless.
The other problem is, the graphit/tech version is prone to snapping if you're not careful when stringing the bass.
Seems like a "nifty" solution to a problem that doesn't really exist, with negative side-effects, IMHO.