This is true. There are only a few vendors out there who support IPv6 at all, and those that do aren't consistent with their products.

For example, D-Link supports IPv6 + tunneling on their DIR-615, but only on revisions C and E (not D), and don't support firewalling for IPv6.

However, most do support radvd for stateless addressing, which OS X supports fine. This is also the easiest option for configuration in home networks.