Dish has CBS in HD. But I think that is the only major network right now.
tburdett, make sure that Comcast can and will give you the local channels in HD. Otherwise you might be stuck with only having the cable channels in HD.
It's a measure of the state of the cable/satellite industry with respect to HDTV; note that the press release is only a month old! Beneath the press release, there is a list of about 20 major cities this agreement affects and then about 20 more that already had some sort of deal in place!
BTW, the AVSForum site is where I get most of my HDTV info. So if I'm wrong, blame them. ;-)
That is good news. I have a friend who just got a HD box through comcast. He said that he likes it. I haven't asked if he has CBS HD, but I know he said he doesn't have UPN or WB HD. I will also ask about ABC and NBC.