I watched ANH the first time through the day it came out and noticed what I thought was a number of audio and video errors. I went online and found other people complaining about the same issues. But then I went back and checked my setup and found my tuner had been F-ed with (I have a 16-month-old son, so go figure). I straightened out my tuner and speakers, and ran the THX setup both for sound and picture and re-watched. Most of the problems went away upon viewing after these steps. Among other key problematic areas, I watched the Tarkin dialogue scene that everybody harps on again (I even turned my tuner down to -60dB) and had no trouble making out the dialogue clearly.
The Subtitles issue that some complain about has more to do with how individual players handle subtitles by default. I always set up my subtitle options on the menu because my player always defaults to a subtitle stream if I don't. Really annoying when you don't want to see subtitles, or if the subtitle order was screwed up in the mastering process. A previous user posted to set the "none" option in the setup menu. I concur. Always run your setup before watching a DVD.
Also, be sure that you select the correct mix for your setup. Many people with a stereo or even a (gasp!) mono TV configuration may select the 5.1 track (it's the default stream, proving that the masses aren't considered in the usability of this disc), and send a generous portion of the mix to speakers that don't exist. If you don't have 5.1, or if it isn't configured correctly, there will be numerous problems. Case in point: In my configuration, I was running the 5.1 into a PCM stereo setting on my tuner, cutting out the center and rears. To top it off, my subwoofer had been plugged into the sub input, not output.
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Frankly, if I ran Hollywood, all DVDs would force a setup menu upon loading, and it would be handled in a much more userfriendly manner. My dad doesn't know what the f a Dolby EX is, but I bet he'd select it because it sounds cool, even though he has a 20-year old RCA television with mono sound.
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I'm guessing some of the audiophiles with correct setups are still noticing some legitimate problems, but I think a LOT of the problems are coming from trying to run the 5.1 mix into a stereo setup.
That said, Lukes saber in the Falcon is undoubtedly green, there are still matte boxes around a few TIE fighter shots in the dogfight, and when Luke says "What good is it if he gets himself killed" the dialogue seems to have jumped up a few dB as if a studio loop wasn't mixed in quite right. Lucasfilm does have some issues to fix and I hope they do a replacement run like they did on the ESB laserdisc a decade ago.