There is different kind of information on changes depending which site/forum you go to. I am concentrating on the stuff that I couldn't detect in my 1080p versions.
www.starwars-union.de (german site) reports stuff like:
- Blue Filter on Hoth got reduced
- Obi Wan Ghost on Hoth can be seen a lot clearer now
- Lightsabers got fixed and are now shiny red and blue, with white cores
- Leia Hologram is more blue
http://www.thedigitalbits.com/ reacted to the official confirm from Lucasfilm on the "Noooo".
On a positive note, it sounds like the A/V quality of these discs is excellent on the whole (at least according to the guys in Europe and China who have apparently gotten their hands on factory-leaked discs. ... As expected, numerous (though not all) picture and sound defects in these films have apparently been corrected. But while it's three steps forward in quality, it may be two and a half back for more changes.
thedigitalbits.com
How can this release be of excellent A/V quality if the video is not a bit different than the 2004 hd master? I am talking about the crushed blacks, oversaturation, contrast-boost, color-timing issues, lightsaber colors.
Numerous picture defects have been corrected? No! We got two half-hearted lightsaber shots (not scenes!) fixed.
Three steps forward in quality? Where exactly?
This thing is 95% the 2004 hd master. 3% difference for less compression artefacts in a/v, 2% difference for content changes.