I watch the ESPN HD channels a lot and have never seen what I saw on Speed HD yesterday, so I still do not believe it is a D* issue. I have seen something similar when watching my local ABC affiliate (also 720p) via my antenna, so that is further proof to me that it is not a D* issue. For my ABC problem (which was judder), I found changing the setting on my Sony TV for Cinemotion fixed the problem without reducing picture quality or motion handling at all. Maybe you need to look at some settings on your TV?
Also, what I saw on Speed yesterday is not what I would consider judder - at least not the same judder I experienced with my local ABC via antenna. My ABC judder was very subtle (my wife couldn't even see it sometimes). On the other hand, what I saw on Speed HD yesterday was very pronounced: the video froze for a second and then jumped back to live. The audio was never lost or frozen or distorted at all. It kind of looked like a web video being played while still downloading where the playback catches up to the buffer and it stops playing until more is downloaded.