IPv6 exists for more than 15 years and it is rumored to be deployed extensively in Asia and especially in Japan and China with Africa being the last continent to deploy IPv6. Another place where there should be a lot of deployments is of course in the USA with the US Government IPv6 mandates.
But, when it comes to measure where web sites are actually deployed over IPv6, the rumor proves to be just a myth. There are multiple studies and researches looking for which web site is reachable over IPv6 and whether the site has a AAAA record in the DNS (AAAA is resource record for an IPv6 address). For a couple of months, I have run yet-another-version of this IPv6-readiness survey for major web sites in several countries (checking the 50 most popular sites in several countries). The daily updated results are:
http://www.vyncke.org/ipv6status/
The analysis differentiates between:
This investigation shows that for same-name dual-stack web sites, this is Netherlands (10% of the sites are IPv6 enabled), Luxembourg, France and Portugal. USA is close with 2% but all Asian countries are far behind: they have not a single dual-stack web site in their top 50 sites. Even more striking: Kenya has indeed a same-name dual-stack web site: http://www.equitybank.co.ke.
The survey for different-name dual-stack is a little more positive: the leaders are still Netherlands but also USA (12% with the obvious sites of http://ipv6.google.com and http://www.v6.facebook.com) and the Czech Republic (also 18%). Japan and China are at the bottom with a meager 2% of their top 50% sites being IPv6 enabled.
Of course, there are a couple of caveats in the above analysis. First, the situation is improving by the week (with a brand new http://www.ipv6.cisco.com for example end of August 2010) also the focus is on web sites which is not a real indicator of the amount of Service Providers and users using IPv6.
The reader interested by this kind of measurement will find at the same http://www.vyncke.org/ipv6status/ statistics about IPv6-enabled email servers and DNS servers.
There are multiple similar surveys: