Not using your ISP's DNS can confound CDNs. In particular, I had to revert to my ISP's DNS servers from Google's specifically because my AppleTV was unable to stream movies otherwise. This was when Google DNS first launched, but you might give it a shot.

I happen to have a router running dnsmasq, so I could use different upstream DNS servers depending upon the query (i.e. route CDN domain queries to my ISP and everything else to Google), but I found it not worth the trouble. TWC's DNS isn't that bad... I do override their search page for non-existant domains with NXDOMAIN however.

This is why anycast is better than DNS for cdn, IMHO :)

How easy is it to set up any cast as opposed to geo-DNS routing?

That's useful information that I didn't know. Thanks for sharing.

That's exactly the reason I haven't switched away from my ISP's DNS because some services do run significantly better over my ISP's DNS instead of the non-ISP ones.