It's a bit wordy, but this article about the silly retcons GL made to the saga in the prequel movies that led him to "fix" the "errors" in the original trilogy is pretty insightful:
http://whatculture.com/film/10-star-wars-retcons-dumb-actually-hurt.php
On the point about the lightsaber battles, I'm really shocked that Lucas has found a way to "speed up" the Obi-wan/Vader duel and add backflipping Vader and Alec Guinness!