I have nothing to add to the reasons why, but I do have to find it kind of funny that someone who is paying money to two different providers for TV service is going to complain about $10. Cancel your Comcast and you'd come out ahead, even paying $10 more for an "HD" broadcast.
Actually not true. If you add in the internet savings, the savings from not having to pay DirecTv for the HD Extra Pak, and Sports pak channels (FSMW, FSS, FSSW,CSS) included in my Comcast package, and the fact I am on a 1 year introductory price, it would actually cost me MORE to drop Comcast.
To be fair, I am probably going to drop DirecTv next year, since Comcast here has many more HD channels I watch, and I doubt DirecTv will add them, and they are no longer offering the Free HD at DirecTv. Not in any hurry tho, have until January 2013.
Tivo Premier XL4, Tivo Premier, Tivo HD whole home on Xfinity HD, SageTv 8 TB Win7 Server -> DVDO Edge-> Denon AVR, Klipsch KB15's/Sharp Aquos 60"