http://test-ipv6.com/
TWC
Test with IPv4 DNS record
ok (0.200s) using ipv4
Test with IPv6 DNS record
ok (0.166s) using ipv6
Test with Dual Stack DNS record
ok (0.355s) using ipv6
Test for Dual Stack DNS and large packet
ok (0.162s) using ipv6
Test IPv4 without DNS
ok (0.335s) using ipv4
Test IPv6 without DNS
ok (0.312s) using ipv6
Test IPv6 large packet
ok (2.636s) using ipv6
Test if your ISP's DNS server uses IPv6
bad (0.511s)
Find IPv4 Service Provider
ok (0.664s) using ipv4 ASN 11426
Find IPv6 Service Provider
ok (0.448s) using ipv6 ASN 11426
TWC (130 miles east of Mackin. Same state)
Test with IPv4 DNS record
ok (0.274s) using ipv4
Test with IPv6 DNS record
bad (0.101s)
Test with Dual Stack DNS record
ok (0.367s) using ipv4
Test for Dual Stack DNS and large packet
ok (0.294s) using ipv4
Test IPv4 without DNS
ok (0.251s) using ipv4
Test IPv6 without DNS
bad (0.072s)
Test IPv6 large packet
bad (0.191s)
Test if your ISP's DNS server uses IPv6
timeout (11.122s)
Find IPv4 Service Provider
ok (0.444s) using ipv4 ASN 11426
Find IPv6 Service Provider
bad (0.146s)
picked it up from this reddit thread
Fix Lollipop wifi issues (and coincidentally the Facebook app) by disabling ipv6
http://www.reddit.com/r/Android/comments/2z1gyo/fix_lollipop_wifi_issues_and_coincidentally_the/
I still haven't heard anybody say anything clever about IPv6 and SEO. Until Google starts to give IPv6 sites a boost the safest bet is to stay on IPv4. If it ain't broken...