Just finished reading a blog post that shows, once again, that people should use their ISP DNS for better performance when it comes to distributed content.
In New Zealand this is even more important because using a local CDN cache gives broadband users a huge advantage instead of fetching resources overseas through a long undersea cable.
There's a dynamic table where you can check the performance loss/gain depending on which CDN you're targeting. Here is one for Australia:
This table shows how much slower a download will be, based on where the CDN is resolved to.
A positive percentage means performance is worse, negative means performance is better. The first one is Google DNS, the second is OpenDNS.
You see now that using those DNS in Australia (and New Zealand, but unfortunately there's no data in the table for our little country) can make things really bad.
Using your ISP DNS will point to the local cache. Using other DNS will instead point to somewhere else in the world.