http://www.bluray-disc.de/blu-ray-news/filme/25089-informationen-zur-deutschen-fassung-von-star-wars-am-16-september-2011-auf-blu-ray-disc
There has been a press event in Hamburg, Germany about the blu-rays.
While the article is in german language it mainly focuses on the work that went in restoring the german audio for this release.
The article speaks about they were showing footage (short scenes from the hexalogy and some bonus content). Besides that it is only PR-bla bla.
1. Lisp problematic
When the german audio was remixed for the 1997 SE, a double-used filter deEsser caused a lisp effect to almost everys actor voice. That was hearable in the cinemas in 1997 and on all SE home video releases and SE broadcasts. The lisp problem was brought up by many fans to Lucasfilm.
The official explanation back then was that the house carrying the 70mm german audio masters burned down and hence inferior sources for the remix have to be used instead.
The 2004 OT DVDs suffer from the same audio problems.
Now with fixing it for the blu-rays they admit there has always been better sources avaiable!
2. Dialog
There are a few scenes in the OT, where some lines of dialog are missing in the german releases.
Yavin 4 - Luke & Han arguing about Han should join the rebellion
According to the article the complete dialog for that scene was recorded and there in the german cinema mix. [comment: But due to unknown reasons it's never fully featured on a single home video release.]
There is another scene, where important dialog is missing. Imagine Leia & Han talking the same but without the sentence 'they are tracking us.' But the article doesn't cover that scene-dialog.
Several lines of dialog from 3PO are missing in ESB on the 2004 OT DVDs, which are featured in the OUT. That needs to be taken care of for the blu-rays.
The best part of the article: there is no kenkraly2007 comment! ;)