I think it's simplistic to say that Moodle is gaining mind share just because of UI. In addition to the UI, it has a number of strengths, among these are:
a) simple installer;
b) excellent documentation;
c) user-driven community;
d) stable platform;
e) clear roadmaps;
OpenACS/.LRN is not even close. We continue to suffer from obscurity, fragmentation, and instability.
The OpenACS core is solid. Otherwise, OpenACS/.LRN is at best devolving into a confusing hodge-podge of poorly maintained packages. Cleaning up the UI and "better marketing" ain't gonna solve the fundamental weaknesses.
