From Ars Technica’s “The future is forever: the state of IPv6 in the Apple world”:

Last year, the Internet Society organized World IPv6 Day, where, among many others, the four biggest Web properties enabled IPv6 for 24 hours. The flushing out of hidden IPv6 problems was pretty successful, so this year’s World IPv6 Launch on June 6 will turn on the new protocol—and then leave it on. The future becoming forever and all.

First the good news:

In late 2008, Google measurements showed that Apple users were ten times as likely to be IPv6-capable than Windows and Linux users.

The article does a great job covering every device in the Apple ecosystem & how ready it is for IPv6. Mostly, they’re ready to go.

And now the bad news:

Because all the routers along the path between two IPv6 systems must be upgraded to provide “native” IPv6, most IPv6 connectivity was based on tunnels until recently. With a tunnel, an IPv6 packet is put inside an IPv4 packet so it can be forwarded by existing IPv4 routers until it reaches an IPv6-capable router again. Windows Vista and Windows 7 have IPv6 turned on out of the box, and will try to use the 6to4 or Teredo tunneling mechanisms to talk to the IPv6 Internet if they can’t find a local IPv6 router. However, these tunneled packets are sometimes filtered and then the systems think they have IPv6… but it doesn’t actually work.

To add insult to injury, Windows makes it exceedingly easy to share such broken IPv6 connectivity over Ethernet or WiFi, creating problems for all users of IPv6-enabled systems. In OS X 10.2 to 10.5, as with pretty much any other IPv6-capable system, IPv6 connectivity is preferred when the local machine has a “real” IPv6 address (not just a local one) and the destination has an IPv6 address in the DNS. So advertising broken IPv6 connectivity means the systems that pick up on that connectivity will try to use it preferentially over IPv4, to their detriment.

Thank you, Microsoft. I’m assuming (perhaps foolishly) that this is fixed in Windows 8.