"Not everything is accessible with NAT64, such as SIP, Skype, MSN, and sites with IPv4 literals.[a] However, 464XLAT RFC 6877,[3] which uses NAT64, allows for such protocols over ipv6 only connections."
Agreed. None of the options for accessing IPv4 only websites via IPv6 only hosts are great. If you are running an IPv4 only website or service this should hopefully worry you.
It would be great if more websites supported IPv6. Like, oh, (cough)(cough)HN(cough)(cough).