I live in Bethel.
I find the residential HSI service to be very good, with regards to both speed and reliability. I get the speeds appropriate for the package I subscribe to. I do not see slowdowns during afternoon or evening hours. Aside from the occasional hurricane or freak snowstorm, the reliability is also very good.
You didn't ask, but I have also found the techs who come to my house to be very good to excellent. I've never had any issues with them or the work they did.
Comcast's customer service, on the other hand, is less than optimum.
[edit: reading further down the thread, there is now upstream channel bonding, but no IPv6 (I use a tunnelbroker.net tunnel for IPv6)]