I think that we know what we're looking at; I know that I'm getting the best available stream because I'm watching on the PS3 and I can ask what the encoding is. (I use the term "shuddering" because I'm not sure that it's actual judder; I haven't seen it on anything in quite a while--I did say that it was something from when they started out. If you want to see what I mean by "shuddering", watch Planet 51). Starz varies in quality from title to title and I have seen things that were STD DVD quality and therefore tolerable--Camelot was not one of them.
EDIT: Unfortunately, Planet 51 is gone and I don't remember another title with the video stuttering problem in motion scenes that was as bad as it was. Believe me, it was a problem on older titles.