Mike,
I think what we've got here are two different issues.
Milo said :
my ISPs DNS server settings (Zen Internet) the downloads fail. If I switch to OpenDNS they work
As far as Akamai is concerned, this should
NEVER happen. It is Akamai's job to distribute the content.... it they cannot reach you at your ISP then that is something they need to be told about via the ISP.
Zen in this instance need to be told something might be up that needs to be looked at which is preventing access to Akamai via their resolvers.
Separately, in terms of what you posted in terms of performance (or lack thereof), I need to re-read it before commenting (or raising it informally with Akamai at some point if nothing stands out). At a first glance, I suspect there may be some over-simplification going on in that blog post.... but as I said, need to re-read with a clear mind at some point !