For me, HE's IPv6 tunnels are "basic Internet infrastructure". This is how I get a real end-to-end IPv6 address, since my ISP doesn't provide one natively.

Earlier this year, their tunnelbroker service went offline due to an expired domain: https://news.ycombinator.com/item?id=47335072

HE doesn't appear to be doing a very good job maintaining this infrastructure.