Local bass player/builder/luthier friend of mine has brass nuts on all his basses.
He is a jazz fan and has built some of the most awesome looking/sounding jazz basses ive come across. Finally sent my pbass to him to get a brass nut custom made and fitted to it.
I guess the best part about it is that it wont wear out like the original black plastic nut that was in it. Actually, the best part is how AWESOME it looks. Ill have to get a photo of it. He hand crafts these bad boys. Looks like a piece of jewelry, not a nut.
At least to my ears, the open notes sound more full and crisp. More similar to a fretted note, which is a bonus! Ive never been a fan of the open A D or G, but now its not an issue!