Brass actually has great tone, but it's a very soft metal so it will wear much quicker than, say, 7075 Aluminum or Stainless Steel. With a
trem block (the part where the springs attach, and the strings go through in this case), I wouldn't worry too much about wear. It basically just sits there. :-)
LGM tossed me a link to some crazy guy building all-brass trems himself, for his guitars. They sure looked nice, and I'll bet they sounded great, but I personally need some major durability in my trems. :-) I'll ask him to post the link here.
