Many of the additions to the '97 SE were things that originated in the mono mix, but hadn't been heard since the original release, since home video versions were always based on the stereo mixes. Things like the "deceleration" sound when the Falcon comes out of lightspeed, the beeping of the gun turrets, the .44 Magnum laser, and "Close the blast doors!" all came from the mono, as well as others I can't think of at the moment. The greater prominence of the music in the '97 mix also reflects the mono as well. Of course, there were many other added sound effects in the SE that had never been in any version of the movie before, and some that made their first appearance in the '93 mix.

But the majority of the differences in the mono mix have still never appeared in any other version--the cantina music heard before they go inside, the alternate dialogue (Aunt Beru, stormtroopers, Death Star intercom voices, different takes of some of Luke's lines, and the complete lack of comm static and radio scrambling during the Battle of Yavin), the beeping of the intercom that starts almost as soon as Luke and Han start shooting in the cell bay, and the stormtrooper in Mos Eisley saying "How long have you had these droids?" about a second earlier, which makes it sound like Luke has to think of a good lie before replying, instead of answering immediately as he does in the stereo version. Some of these little details add to the aural immersion, giving it a more complete and unified feeling, though some of the changes come across as strange and heavy-handed to me. To each his own, I guess--as long as we've got them all to choose from.