We have been measuring the number of clients connecting to www.ripe.net over IPv6 and made some interesting observations.
The percentage of users using IPv6 to connect to www.ripe.net for the last month is a bit atypical, which is good news and bad news. The bad news is that overall growth seems to stagnate a bit. The good news is that native IPv6 usage is still increasing and we see a drop in 6to4 (represented as a blue line on Figure 1 below). It looks like this is caused by the release of a new version of the Opera web browser early in March 2010, which doesn't prefer tunneled IPv6 (like 6to4 or Teredo) over IPv4 anymore. This is a good thing, but it has this strange effect on the IPv6 usage of clients as seen from web servers.
Figure 1: Percentage of clients connecting to www.ripe.net via IPv6 (daily bins)