Hey, so I had posted the above primarily because I've been trying to get a routable IPv6 address for a while, and haven't been successful; I've repeatedly asked Comcast when my CMTS would be IPv6 enabled, but their techs have just said "try enabling IPv6 on your computer and see if it works", they haven't been able to give me a schedule or even tell me if it was supposed to work yet.

However, just checked last night and discovered that they'd added a new feature that would tell you when your CMTS was IPv6 ready, and it turns out that they've finally upgraded me. I could finally switch off my tunnel and use a real, routable address. Woo!