Thanks for all the quick replies. I was wondering if anyone knows what or how Comcasts HD quality is? Do they compress their signal?
How many of Direct Tv's HD channels actually broadcast HD material? Like CNN, Disney, Bravo, CMT, Nick, etc?
What they broadcast is purely dependent on what the networks provide.
That being said, there are several available HD channels that seem nothing more than "placeholders" for future HD expansion: MTV, VH-1, CMT, Cartoon Network and Fuel all come to mind.
Channels like CNN, The Weather Channel, Bravo and others offer a mix of HD and SD programming - some more HD than others.
The Discovery Networks are all on my bad list at the moment. They have far less true HD content than one would think and compensate by doing a 14:9 partial zoom on the SD content, cutting off the top and bottom of the picture. It's really not that bad until text gets cut off, but..
If you have a TV that can "squeeze" a 16:9 widescreen picture back to 4:3, you can get good 4:3 PQ off SD progams on TBS, A&E, Bio, History and Cartoon Network who all stretch SD programming to fill the 16:9 screen.
Of course, all these foibles are true no matter what provder you pick.
I'll tell you, so far I've been impressed the most with Toon Disney, Speed and USA. They seem to have more HD programming than I personally would have expected. TBS is coming along, as well. MGM HD is awesome looking if you're into movies, too.