HD radio is pretty cool. It's like regular radio only better sounding. When compared to XM or Sirius you don't get nearly as much selection, because you're still limited to the same frequency bands as regular FM. But like in the picture, you do get sub channels for some stations. A few people are looking to plug their Zunes into their cars, sync via wi-fi and forget, so yeah I'm trying to keep up on the head unit news too. So I guess a Zune HD + Zune capable head unit is the next best thing.
So the Terrain will recognize some Zunes but not others? I just read ecolodge's issue about the Zune 8 being finicky (http://www.terrainforum.net/index.php?topic=217.0). But any other reports? I'll ask and see if I can get a list of what vehicles are supported. Also (off topic) what don't you like about the Zune software (PM maybe?)?
No Pioneer units in these cars.