TiPb's gotten lots of reports from iPhone, iPad and Apple TV users of super slow iTunes rentals and downloads -- we're talking hours and hours! -- and it looks like Google DNS (and OpenDNS) could be part of the problem. According to Joe Mailer:
This totally makes sense. iTunes’ video content is delivered by Akamai who has distributed massive datastores around the world so those large files originate from nearby servers and spend less time getting switched around the network. Akamai somehow uses our DNS routing to determine our location. If Google DNS or OpenDNS routes everyone to Akamai the same way, then those Akamai nodes and the pipes leading to them get overwhelmed.
So if your iPhone, iPod touch, iPad or Apple TV tells you there are 2+ hours to go before you can start watching check to see if you're using Google DNS or OpenDNS and try switching to your IPs DNS instead. It could cut your wait times down to seconds!