On June 8 2011 there was the first full scale test of IPv6. There was no major problem and only a few people encountered some difficulties. One year later almost to the day, June 6 2012 - tomorrow - will be the first day of the IPv6 Internet era.
From Wednesday, most of the biggest Internet services such as Google, Comcast, Cisco, etc. will all switch to IPv6. It doesn't mean that IPv4 will stop working, it probably won't happen before a long time, only that a device without an IPv4 will be able to connect to these services.
The situation was becoming critical because all 232 available IPv4 addresses have been attributed or reserved while there are ever more devices that need to connect, computers, tablets, smartphones of course but also more and more toys and home appliances.
IPv6 support a maximum of 2128 addresses, a new limit that will benearly impossible to reach.
If your internet provider supports IPv6 and that you have an Airport base and a Mac, you will be able to use IPv6 without any problem. If you havent configured your Aiport base, be aware that Aiport Utility version 6.0 doesn't allow the configuration of IPv6, an omission that should be corrected soon by Apple. For now, you can get version 5.6 here: http://support.apple.com/kb/DL1482. The only difference with version 6.0 is the iCloud configuration option.
By Machmeter, original by Lionel