Hi, and sorry for the delay in responding! It IS a broad question, and I have hesitated to respond, my mind flooded with the numerous issues that a broad question such as this raises.
In the end, I settled on focusing my answer to the following, and if you need to ask more, please do so.
IPv6 is well into deployment.
IPv6 is available in Mac OS X 10.2 Jaguar. Linux kernels version 2.2 and above ship with an IPv6 implementation built in. (Same goes for Solaris and many others). Microsoft Windows XP includes an IPv6 implementation intended for development use and trial network deployments. It has been standard in Vista and Windows 7.
Every main operating system for computing supports IPv6 by default (Windows, Linux, MAC, etc). So it is safe to say that end users are fairly well positioned as long as they are using a newer version of their OS's.
The IPv6 core network has been established and is growing steadily in capacity and traffic carried. Sometimes called the 6bone, and sometimes called Internet2; see a topology of the 6bone network here:http://www.dbnet.ece.ntua.gr/6bone/
Just about every Router/Switch manufacturer has supported IPv6 for a number of years now (Cisco since 12.2(T) for example).
We are tired of the "Chicken Little" types that keep forecasting the death of IPv4. So far not one of the predictions have come true. We also see that there is a tremendous amount of hoarding of IPv4 addresses (nothing against any of these folks but one has to wonder why MIT needs 16 million IPv4 addresses, or HP needing 32 million?).
Nonetheless, we cannot ignore the growth of the Internet address consumption.
So we say it is time to prepare for IPv6.
Any routers or switches you purchase for your network should be IPv6 compliant.
You should be developing an IPv6 strategy (yes, we would love to help!)
You should also start to learn about IPv6 if you are a tier 2 or tier 3 service provider. One way (forgive us blowing our own horns here) is to get into a hands on class on the subject.
We hope this helps, and I welcome further discussion!