Ok, I just spent a good long while checking the ESB file. For the most part it seems good, but it still needs a bit of work. I haven't actually checked the whole film, but I went through enough of it to make informed observations.
I noticed the sound at the start that was already pointed out, but it would be relatively simple to replace that with silence. Compared to the '93 mix, the very beginning of the Fox fanfare seems to be missing--no idea whether it was an error in capturing or if the laserdisc itself is like that. It's only a small fragment of the music, but noticeable.
The synch varies with time as the movie goes along. Sometimes it is very close, differing from the '93 mix by as little as 2 milliseconds, but often it lags behind by nearly 40 milliseconds, which is approximately equivalent to one frame of film. As I suspected, the loss of synch often occurs around the reel change times that Darth Mallwalker posted. I'm not sure exactly how much of a problem this actually is, practically speaking--some people may notice it, others may not. I've only been comparing the audio tracks to each other, not with the video, so I can't comment on that directly.
There is one definite error that is in need of fixing, and this occurs at the break between sides 4 and 5 of the LD. Side 4 ends just as the door to the carbon freeze chamber shuts behind Luke, with side 5 beginning as he is brought up into the room before he meets Vader. There is a significant gap of silence, approximately 0.076 seconds in length, which creates a distracting jump cut in the sound. This is probably not directly fixable from the laserdisc alone, due to missing frames around the side change. To create a seamless bridge between the sides, another mix would have to be used to patch over this section.
If you are referring to the two ignition sounds when Luke reaches his lightsaber in the wampa cave, the 35mm mix has always sounded this way--it may be an error, but one on the part of the film mixers themselves if so. The splashing sound in the Dagobah cave has likewise always been there. Observations of improved ambience in the 35mm mix as compared to the '93 are explainable in two ways. One, as has been stated, the dynamic limiting means that the quieter sounds are elevated, allowing them to be heard more prominently; a similar immersion can probably be achieved from the '93 if the gain is raised to bring the average volume to the same level (which will also make the much higher dynamic peaks of the '93 mix that much more noticeable). Two, the EQ of the 35mm version is different, placing more emphasis on the higher frequencies, which lends itself to greater detection of small background sounds. Ultimately I prefer the more robust EQ of the '93 version, but your mileage may vary.
I did notice that there is a fair amount of high frequency noise throughout the whole thing, most evident during quiet sections. It sounds like tape hiss some of the time, but I think the analog equipment used to play and capture the audio from the laserdisc is the most likely culprit. How much of an issue that is to d_j or to listeners, I don't know.
Been discussing this mix with Darth Mallwalker, and I'm going to compare it to a digital version from a later laserdisc release, to try to determine whether the same 35mm mix was always used before 1993 or whether it was remixed in 1985 as ANH was (I believe it was probably not remixed, but I haven't heard it yet). It sounds like he's got a high quality capture setup, so I'm probably going to end up synching this myself based on his files and on the reel change times he indicated. dark_jedi, would you prefer to wait for me to do that or use your own for the dvd?
Either way, I'm still doing the music-edited 5.1--just got a bit distracted from it. :)