"I find the American channel use of sub channels a little wierd. What's this sub channel thing all about?"
If you are talking about OTA Multichannels which appear as -1,thru -5 than some stations use them wisely. The best example is my local PBS station "UPN" here in Raleigh,NC
Depending on the time of day UPN shows 4-1,4-3,4-4,4-4 or they show 4-1,4-2,4-3
4-1 typically is the same as analog PBS and in 4:3 format. 4-2 is their HD channel and has some real nice HD shows broadcast typically in the evenings in 16:9 mode. Some times 4-1 will be the same broadcast as 4-2 but not HD. 4-3 is always children shows 4-4 and 4-5 can be talk,cartoons,nature or whatever but are always low res 4:3 and not HD.
Just last night the 4-1 was busy raising money and 4-2 was showing a good HD show about Snowflake a white Gorrilla. Not all of it was in HD but most of it was.
If you switched to analog PBS all you would get is the raisng money broadcast. Of course I know that is what keeps them on the air !!!
I caught PAX for the first time over the weekend. 47-1 PAX same as Analog Pax 47-2 PAXWEST 47-3 Worship 47-4 Faith.
I don't think any of the PAX line up at the time I watched it was true HD.
Most of the major networks such as ABC,CBS,NBC, and Fox use channel -1 for HD 16:9, and Channel -2 for 4:3 version, -3 for local weather.
As long as they keep broadcasting HD 16:9 I kind of like the Simulcast channels. I just wish that the major networks would see fit to rebroadcast 4:3 CNN,History,AMC, or some other popular cable network. But not sure if they could ever get the revenue figured out.
Usually I find that the 4:3 in a stretched mode looks pretty good. I realise that simulcast channels rob bandwidth from the overall 16:9 HD widescreen experience, But so far I have not been dissapointed. Maybe someone else has or maybe someone else has found that the surround sound is lacking. I can speak to surround sound.