Here in the CentOS Project, we like ipv6.
In 2007 some of the private CentOS services started moving to ipv6; the entire buildservice has been ipv6 native since Sept 2008.
In 2009 we had mirrorlist.centos.org running over ipv6, which meant essentially the entire CentOS mirror network had ipv6 native support. This isnt something for dualstacked machines – even machines without an ipv4 address were completely supported.
In 2011 we had torrent.centos.org offering an ipv6 hosted tracker service, and a couple of seeds offering content natively on ipv6.
Most, if not all, this ipv6 work is driven by the efforts of Anssi Johansson.
And I also want to take this opportunity to thank two of our long term supporters who have provided us the resources to offer these ipv6 services. Coreix.net since 2007 and more recently UK2.net since 2011.