As a long-term user of SixXS, I got an e-mail earlier this year about how I should stop using a tunnel for IPv6 connectivity and ask my ISP for IPv6. And they've got a point. After all, now that major bandwidth hogs such as Netflix and Facebook have IPv6 enabled, those tunnels must be shifting some serious traffic.
Having said that, Netflix have recently started proclaiming Sixxs is a "proxy service" which they can't allow because it lets you pretend to be in the UK wherever in the world you are. Which is fair enough if tedious, and has forced me to move my TV-connected devices onto my guest WiFi network, where there is no IPv6.