ARIN and the Cooperative Association for Internet Data Analysis (CAIDA) worked together to conduct a survey to capture IPv6 penetration data in the ARIN region. The survey took place in March of 2008 and an analysis of the results was presented by kc claffy of CAIDA during the ARIN XXI meeting in Denver, Colorado, last week.
You can find the link to this presentation on the top-right corner of ARIN's IPv6 wiki at:
Below are links to kc claffy's presentation of the results, and a copy of the survey questions and possible responses. Both documents are in PDF format.