Oh, many things could be affecting the ping time. The only reason why IPv6 would be affecting the ping time is because fewer people are using those routers and servers.

Besides, once you get to ipv6.google.com, you will notice that most of their links point to www.google.com, which is uses an IPv4 address. There is very little reason for us to care about IPv6 websites until we actually have an IPv6 address ourselves (rather than running through 6to4).
QUOTE(quantumAlpha @ Jun 22 2008, 00:17)

either comcast isn't ipv6 compatible yet (likely)
or OpenDNS has issues with ipv6 name resolution (likely)
anyone have the ipv6 address for ipv6.google.com? i'd like to give it a shot
On a Vista computer, try accessing ipv6.google.com when you have a direct connection to the Internet (rather than going through a NAT router). Your ISP is still giving you an IPv4 address, but Vista has 6to4 enabled. This can be done on XP also, but I think you would have to setup the IPv6 protocol first.