DJB was wrong... even if he was right too.

You can test almost everything via a tunnel. The various _automatic_ tunnels which other people have mentioned all use your IPv4 address in order to assign you an IPv6 unicast subnet for your use.

In this scenario you are an IPv6 island, connected to other IPv6 islands by tunnel. If they _wanted to_ ISPs could compete by providing a tunnel endpoint closer to their subscribers, so IPv6 would work faster on their network than on a competitors. Technologies like 6to4 even made this very easy by using an anycast address, so the ISP can put the tunnel endpoint anywhere with no config change for the user. The natural endpoint of such competition would be native IPv6, no tunnels.

But the major ISPs as we've tried repeatedly to explain, do not care. If the closest endpoint is on another continent, why should they care? Providing the minimum possible service is a cost saving. So if you try to use such a tunnel, expect poor performance and zero technical support from your ISP. It's just not in their interest to care.

Have I told the story about the cable TV company who added a "digital surcharge" to pay for equipment upgrades ready for digital cable? I bet you're thinking that they had to do that - to pay for the upgrades, right? Nope, there were no upgrades. It was just another way to get more money. When digital cable actually arrived they couldn't offer it, because their equipment was too old. No matter, the customers still have money, just charge them again.