I have enabled and used ipv6 on a number of machines, I did have this website enabled at one stage but due to the ipv6 pop being down for several months now, I deleted the AAA record from my DNS . I have my account and all my ipv6 tunnels with SIXXS using Heanet and OCCAID Inc. I never had a problem with Heanet so far, but occaid reliability has left me wondering if ipv6 at its basic level (tunneling) is ever going to get better. I have had to apply for two tunnels so far as occaid first pop that I chose has being Offline now for 8+ months now and their second pop is off line for at least 4+months with no fix time allocated. I could switch ipv6 broker again 
There is a big push in the networking community to get ipv6 up and running and to get as many users using ipv6 but what happens when a pop goes down and all the feed back that is given is: tunnel broker has been notified. Sorry for seem sarcastic but Wow that useful information, a fix date would be better! Also I have noted before, asking such question to sixxs support people get rude or not very informative replies.
I do know that sixxs are offering a free service and they do rely on the pop ISP to make the service avaialble, I suppose when you have to go through the process of applying for a new tunnel changing ipv6 DNS records, changing the tunnel information in /etc/network/interfaces. It can be a Inconvenience and frustrating experience.
I will as of today apply for my third tunnel through another broker in the US. Sigh!