Bought this eMTA modem (for use with digital internet and phone) after Comcast told me I would be charge a $7/month rental fee automatically for using theirs. They said that this modem was not sold anywhere, but that if I found one that was compatible, it would work and the fee would be waved. When the installation technician (a contractor who is not an employee of Comcast) came to set up my phone and cable, they hassled him about the modem, but he was on my side and made it work.
According to Comcast's website, there are only SOME geographic areas where they allow you to use your own eMTA modem, but they do not say what those areas are (I am in the Northwest Seattle area). I suspect that if you have an installation technician who does not work for Comcast, you will have no problem getting this thing to work for you.
Another note the thing looks and feels big and bulky, so if something "sleek" is what you are looking for, this is not the modem for you. Integrated battery back up is great if the power goes out, you will still have phone service.
Comcast is working with Motorola to come out with self install kits so you cannot use your own EMTA unit until that process is completed.