I agree with this. However, Lucas is capable of writing great dialogue as well, it's just not his strongest suit. (And let's not forget that a lot of the "brilliant" dialogue from Empire was in fact changed on set, and not writen by Kasdan). I'm not thinking about disagreements, but they way the structure of the story changed because of the story conferences. The early scripts by Lucas were quite different in many substantial ways: Leia went on a solo mission to Endor, Han's rescue wasn't an independent first act, Vader was much more of an anti-hero, Moff Jerjerrod had a prominent role, Luke didn't go back to Dagobah, there was Had Abbadon (the capital of the Empire), two Death Stars.... The ELEMENTS of the story (Jabba, The Emperor, the Ewoks) didn't change, but the structure of the story changed radically after the conferences with Kasdan (therefore, he must've had an influence on that). In fact, Lucas had to write a very basic summary/list of scenes after the conferences were over, because the new script by Kasdan would be very different from the early scripts by Lucas. With Empire, Lucas' second draft was already close to the final script except for the actual dialogue of the scenes. The story conferences with Kasdan and Kershner didn't have any impact on the strucure of the story.