That's my personal favourite mix since I was used to it for years on VHS, and is part of why I wanted to get the editdroid.
Heh. I was actually thinking of starting a thread like this myself, but I was beaten to it. lol
There are a lot of other subtle differences between the mixes that I'm not sure I've seen anyone point out yet, particularly in the beginning of the movie:
As the Star Destroyer flies about halfway overhead there is a bright flash of light that on the old stereo is not accompanied by any sort of explosive sound effect. On the '93 THX one was added; the '97 special edition supercedes it with a longer, higher-pitched and more "stereo-ized" explosion sound. I don't know if the mono had any sound there or not, as I've never had an opportunity to hear the mono. I would guess it does, since it has other sounds that the early stereo does not. It makes sense to have a sound to accompany the flash, but I kind of like it without.
The Star Destroyer's flight seems to have more bass rumble on the '93 than on the '85, though it is not intrusive. (The 2004 dvd adds an absurd amount of bass here, as well as throughout the entire film, making many sounds come out overworked and wrong.)
The music is heard far more prominently in the '97 special edition mix than in any others. I like it this way.
The Imperial turbolaser blasts sound less 'zingy' in the special edition. Picturewise the blasts also appear narrower in the opening shot, interestingly. (In the '04 they are white! instead of green.)
The '93 adds a loud turbolaser effect when the Tantive is hit. This does not appear on any other mix I am aware of. Not sure of the mono, again.
More explosive sounds are heard aboard the Tantive after it is hit in the special edition, and at different volume levels. More sound effects of the ship being secured in the hangar (as the Rebel troops look around at the ceiling) are heard.
The '85 mix does not feature the low rumbling sound right before the Imperials start to blast their way through the wall. It is present on the '93 and in the special edition; anyone know if it's on the mono? This effect lets you know something is about to happen; its absence may actually make for greater tension, since you don't know what's going to happen next. The music is heard better without it for that few seconds as well (the way it's composed leads me to believe a few seconds of near-silence was what Williams was writing for in the sound mix).
The explosion of the wall is very forceful on the '85 mix and even more so in the special edition. The '93 THX adds more bass but the overall force and power of the sound effect is reduced, strangely. (The '04, again, adds too much bass, and similarly it is actually a less powerful effect.)
The rhythm of the laser battle in the corridor is completely botched in the '04. I can't even make out what they did to it, it's so bad.
Well, that's the scene I've analyzed most exhaustively on the various mixes. Perhaps I will return to talk about other scenes later on. Heh.