DNS Anycast as traffic optimizer?

[Steve Francis <sfrancis () fastclick com>]

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