I know about the rear channels being reversed
the 'there's no one here' line added to the stormtroopers on the falcon, the crap 'bong' as his head hits the door, the fanfare being too low on the trench dive.
are there any others?
also, anyone got a list of bits of dialogue or sound that were below par on the DVD release, I recall tarkin having a dodgy line that drew some comment.