I just read an article in my local paper that states the smithsonian channel will debut in HD on Wed. of this week. hopefully that will correspond with the other channels.
The Smithsonian Channel will be part of a high-definition extra tier at $4.99 a month, added to the high-definition activation charge of $9.99 a month and the programming package that costs from $29.99 a month.
The channel is grandfathered until the end of the year. Then the channels like HDNet and UHD, including Smithsonian HD, that don't have a corresponding SD channel will cost an extra $4.99/month. There is also a new channel MGM HD which sounds very nice.