Updated July 6, 2006
Satellite may be all digital, but it's not all digital TV. Like "digital" cable, "all digital" satellite refers to the transmission format, not the programming.
But some satellite programming is digital, high-definition widescreen (HDNet, HBO-HD and Discovery HD Theater, etc.), and more is on the way.
Of the two main satellite providers, DirecTV has the advantage with two new satellites launched in 2005 to provide local broadcast stations in high definition to twelve major markets. There are a bunch more now.
Two more satelliite will be launched in 2007 which will add the capability to deliver 1500 additional high-definition channels (local channels in all major markets as well as 150 national channels).
But to reach this capacity, DirecTV has switched from the MPEG-2 video compression protocol to the much more efficient MPEG-4. Unfortunately, MPEG-4 will not work with older DirecTV high-definition systems (antenna and receiver), and these will have to be replaced by subscribers wanting to get the new high-definition channels.
Eventually, all of DirecTV's high-definition content will be converted to MPEG-4 which means all current HD equipment will have to be replaced.
The Dish Network has its own hi-def capable satellites on the way. Check with both providers for current availability, as always.
Dish Network is reportedly also moving to MPEG-4, but their equipment upgrades are included in the cost of the programming.