[grumbling about time limit on editing message...]
It turns out I was wrong and there are two other channels on tr.31.
Actually, there seems to be a significant amount of space on several of the transponders. The most number of HD channels is on tr. 30 - there are 6 HD channels, although 2 (or 3) are 720p.
tr 6 - only 3 HD channels
tr 11 - only 3 HD channels
tr 22 - only 3 HD channels
tr 23 - only 3 HD channels
tr 27 - only 3 HD channels
tr 31 - only 3 HD channels
So, one HD channel could certainly be added to each of those 6 transponders.
I bet we get MTV HD, History Channel HD, Discovery Channel HD, Science Channel HD, TLC HD and 1 of the new Starz HD channels.
Discovery Channel HD is going to replace the current Discovery HD Theater, which will cease operation when Discovery Channel HD starts.
Instead, I'm sure we will get Weather Channel HD, since the channel rep informally stated that Dish will be carrying it soon after launch. Actually, that will probably be one of the better HD channels - because it will actually have new and original HD programming 24/7. In contrast, take National Geographic HD channel, which actually shows a lot of SD programming, plus some of their "HD" programming is interviews in a studio in HD that introduces old footage that is not only SD, it is zoomed to fit the widescreen, so the resolution is actually less than 480.
So Weather Channel HD should actually be a very good use of HD - especially if it means the extra width allows the gal to avoid standing in front of California !