You would need to use either a set-top box or a CableCARD to receive non- broadcast Comcast Digital Cable and/or HDTV channels that are.
I mean I don't expect Comcast HD to be DirecTV HD image quality, no, I am not trying to insult your intelligence but what setting is on the HD Box Resolution wise ?? Therefore they just don't notice Comcast's PQ sucks.
I tried the Xfinity Instant TV ($18), and it was just awful. The thing that turned I add say NBC HD, and there is like 6 of them in SD and HD. There was no way to .