Larry,
I have digatal cable from Time Warrner. Some of the HBO movies are in 5.1 Now don't get your hopes up. Not all of them are. Just some of the new ones. Most are in 2.0DD It is nice, just make sure you don't run your coax thru a surge protector. I did, and I didn't get some of the channels.
They also just started with the HBOHD and CINXHD hi-def channeles. I don't know how they are, since I don't have a hi-def TV yet.