I beg to differ. I've got Comcast in the PNW, and their IPv6 stack on Business class is atrocious. A short list of the issues I've had/am currently experiencing:

- Account is registered for a /56, their router only responds to requests for a /59

- Once my CPE is configured for that /59, routing from anything smaller than that /59 is just dropped on the ground (no delegation to/from /64s, etc, is allowed)

- significant investigation later, the root cause is because I also have a /29 static v4 block on my router. Removing the v4 block from the Comcast end, everything works great (as a /59). As soon as the Comcast equipment receives the static v4 config, v6 delegation grinds to a halt

- Comcast Business Support is WOEFULLY under-trained on v6. Talking about v6 netblocks gets me strange stares and "But I see your /29 on the account, is that what you're talking about?"

- Comcast line-managers have told me on multiple occasions, "Oh, if static-v4/v6 doesn't work, then it's just not supported. Sorry, just take your business elsewhere if static is important to you"