I'm getting rather sick of reading posts along the lines of "it doesn't work," "it'll never work," and "you need to have one work for the other."
In 2006-2007, I tried deploying an IPv4-based TINC setup on my office computers. However, to maintain this, you needed a computer at each of the bigger sites, and smaller systems tied to a common system: I had over 100 nodes chained together like this. By summer 2007, it was unsustainable: I had already been researching IPv6, and decided to start implementing it as a solution for accessing things like Intranet, VNC, and remote file systems. By the end of 2007, I had more or less eliminated the IPv4 chains with a setup of our sites using NAT'd IPv4 in the 192.168-whatever range, and individual IPv6 subnets for each site, tied together by an ethernet-based TINC install on OpenWRT routers. It has worked above and beyond my expectations: we can use regular Internet; we can use IPv6 global and internal resources. If it doesn't support v6 out of the box, chances are it works with "portproxy" fine. With a transition to newer Linux systems and Vista/2008 Windows systems, it becomes more streamlined.
You can't avoid v6: its all around you. I believe in it and I've made it work.
