The only one I remember that he's specifically addressed is the "Han shot first" issue. He said that in the first movie, Han was a badass renegade, certainly not above shooting some bounty hunter if it meant he gets out of there alive. But over the course of the trilogy, he becomes a hero as much as Luke and the others, and he had trouble with Han shooting a guy in cold blood like that. So he changed it to make Greedo shoot first.
This of course inadvertently reveals what we've suspected all along: that Lucas didn't have some "grand plan" in mind for the trilogy or six or nine films as he's said at various times. Also, damn, the original re-edit was horrible. For a professional bounty hunter, Greedo was a horrible shot. The version out there now is almost believeable, but still pretty bad.