Odd. Requires a
little bit of buggering around to get it rolling (for me it'll work on wired/wireless as long as only one is enabled) otherwise you end up with cases where DNS lookups work but you can't browse the site.
The problem I have is that even if you change the prefix list to get Windows 7 to prefer IPv6 native, then 6to4, then Teredo, then everything IPv4 below in priority it'll still prefer IPv4 if both are available. With Firefox's ShowIP addon it might indicate the IPv6 address even if you're using IPv4. But still, some kind of access to IPv6-only is nice, and
this test is smart enough to detect the tunnel where other sites fail.