That's what I'm hearing. Cogent refuses to peer with HE via IPv6. So cogent IPv6 Customers currently can not hit things at HE. And they can't do anything about it. Besides 6to4 tunneling and BGP peering with HE (or native, If they can).
A few weeks ago I compared what cogent sees compared to a tata+highwinds feed.
http://blog.snijders-it.nl/2010/10/cogent-as174-does-not-have-full-ipv6.html
They are missing roughly 1000 prefixes.
As long as we are in public "naming and shaming" mode, it should be noted that Cogent is not alone. We have an IPv4/IPv6 transit from Level3, and they don't have the HE prefixes either. Our two other IPv4/IPv6 transits seem to have no problem supplying us with a full IPv6 routing table. Steinar Haug, Nethelp consulting, sthaug@nethelp.no