I still have more information to add to this, but I didn't want to miss the discussion in this thread. The truth about Empire is something that really gets to me because so many people just believe without question that Lucas was responsible for it all, when in actuality he was an absentee landlord on ESB through and through. It is my personal feeling that Empire is the film he resents the most. I remember interviews with him about the 1997 Special Editions where he said there wasn't much he could do with ESB as far as changes. He spoke as if it were a positive thing, but behind his voice I remember some hesitation.
On top of that, ESB remains the only film to have a "Special Edition" decision reversed - Luke's scream (which just happened to be The Emperor's scream in ROTJ) I expect Lucas is rather resentful about that too - He had to eat crow and change something back the way it originally was...