DNS Anycast as traffic optimizer?

I'm sure there is research out there, but I can't find it, so does anyone know of any research showing how good/bad using DNS anycast is as a kludgey traffic optimiser? (i.e. having multiple datacenters, all anycasting the authoritative name server for a domain, but each datacenters' DNS server resolving the domain name to an IP local to that datacenter, under the assumption that if the end user hit that DNS server first, there is "some" relationship between that datacenter and good performance for that user.) THe question is, what is that "some" relationship? 80% as good as Akamai? Terrible? TIA