Joe Mailer wanted to download an iTunes movie recently and his Apple TV told him it would take two hours. When he switched his DNS resolver settings, the download time dropped to less than 20 seconds. Apparently, iTunes content is served by Akamai which uses geolocation based on the IP address of the DNS request to determine which server should provide his content. When you use Google or Open DNS to resolve the Apple domain name, all the requests to Akamai appear to be coming from the same location and they're all directed to the same server pool, overloading that pool and causing the slow downloads. The solution: Be wary of using Google or Open DNS when downloading iTunes files or similar large files. Use your own ISP's DNS servers instead or run your own resolving DNS server.

http://apple.slashdot.org/story/10/1...DNS-For-iTunes