I started a similar thread recently for all three films here: http://originaltrilogy.com/forum/topic.cfm/70mm-6-Track-Dolby-Stereo-mix-differences/topic/14058/

Like TServo, I also hear Lando's line as a different take compared to what is heard in the 35mm. Also, the sound effect for the TIE's after Luke's failure in the cave are definitely different in the 70mm mix vs. the 35mm mix, what's heard on the foreign tracks on the '06 bonus DVD match the 70mm, the SE is similar but sound a little bit different.

Very interesting find about the difference in audio length in the wampa cave! Should be quite easy to check exactly what shot was added to the 35mm cut after a little closer comparison, nice. :)