I'm in almost the exact same position, except that I didn't know I had v6 access until I happened to think of the IPv6 launch sometime last week, wondered if I was online with it yet, and tried it by enabling it on the AirPort base station. It works perfectly: no glitches, as fast as v4, gets v4, v4/v6, and v6 sites perfectly. It does, as you say, just work.

Props to Comcast for putting the future of the internet into their customers' hands.