Value of IPv6? Well, it provides a whole bunch of benefits. I won't enumerate them here since I'm a little rusty with the list.

Why has it taken off with large providers in the U.S.? Because for a few years now, it has been a mandatory prerequisite for certain U.S. Department of Defense contract bid checklists. If you didn't support it, you couldn't bid for lucrative government (DoD) contracts.

Why has it taken off in Japan? Well, years ago, the entire Internet was essentially divided into regions. A RIR would then allocate its region's block to providers in the region.

Japan had a greater population density and greater use of IPv4 IPs, percentage-wise, so they were really feeling IPv4 pressure. NAT'ing went ever so far. They're also pretty good with technology so trying IPv6 wasn't a hard sell. This helped to ease a lot of the IP addressing pressure.

In the U.S., originally, we were going to run out of IPv4 addresses which was the original impetus for adopting IPv6. However, we seem to have hit a plateau with IPv4 so the major pressure is not quite there any more. Still a potential threat lurking in the background but not as urgent now.

IPv6 addressing space is HUGE!!!! I have an obscenely-sized netblock allocated to me -- the smallest that could be sanely routed, at work. This affords me ability to do all sorts of good subnet allocations and effective firewall filtering.

IPv6 also has a concept of autoconfiguration/router discovery. It's kinda DHCP-like and nice because it just 'works'. Has a bunch of other features. It's a nice skill to learn (for setup) if you ever want to work in Europe/Asia or in the U.S. at a DoD contractor or bidder.

IPv6 is actually now reasonably stable. Cisco, Juniper, I think also Huawei, etc. all supports IPv6 in their main router code now. Pretty much any OS released in the past year or two supports it out of box. This includes: Windows Vista, MacOS X, Linux, OpenVMS, AIX, Solaris, etc.

There are still some quirks in setting up apps to support IPv6 but not too bad. I spent one very intensive weekend with another person at work setting up (from scratch) IPv6-enabled apps, configuring them, ironing out bugs, testing on various platforms. I tested with OpenBSD, Linux, Solaris, AIX, and Windows. All worked great.

So... for most people, there is no real need or reason to play with IPv6. But for some, it's an interesting new skill to master and looks good on a resume/CV as an 'advanced' technical skill that few knows.

P.S. To test if you're connected via IPv6, go to http://www.kame.net
If it's IPv6, the turtle will be dancing.

Unfortunately, v6 isn't going to see widespread adoption until perhaps when v4 address space exhausts. For many places, management works on a 'next crisis' basis.

If I had to guess, the initial approach to v4 address space exhaustion might actually be increased v4 NAT'ing.