Speaking strictly SD, E* is terrible. Some channels are terribly compressed, most noticeable on dark scenes where black levels are washed out and mostly grey.
I finally got around to watching The Aviator from the Starz free preview weekend. There was one dark scene and you can see all the rainbow artifacts when Dicaprio walks. This also happens on Spike TV reruns of DS9.
I do not have D* so I can't compare. But if these SD channels can get bad what is stopping Dish from doing this to the HD channels?