I'm not very familiar with NameServers. Where can I find information or how can I set up multiple servers with different IP's to use the same domain name, such that the client connects to the closest/lowest latency server? I'm having a tough time find the answer to this. It seems like it would be a fairly popular thing to do.
BIND has a GeoIP plugin which, I believe, can allow you to change the response based on the user's location.
An easier solution would be to use Amazon's Route53 DNS service which supports responding differently in different zones, record/set weighting, etc.