Yep, they were shown (or at least parts). They showed lots of material at a press event a few weeks back, but there's an embargo on reviews or previews up at the moment. The discs themselves should hit replication in a week or two and then I'd expect tons of screens/confirmations to finally hit. The best online resource is the mega-thread at Home Theater Forum:HTF Star Wars DVD
The first post is updated whenever new info arrives.
It's a good source for debunking a lot of the wilder rumors, and some decent conversation rationalizing what does seem to have been changed/added.
- Effects reworks include saber effects in ANH, optical matteline removal in all 3 (ships, Rancor)
- Cantina "Greedo shoots first" scene has been reworked with better timing and a new Han reaction. Video was leaked some weeks back.
- Docking Bay 5 Jabba scene still rumored to include a re-rigged CGI Jabba based on the TPM-era model.
- Vader's ESB transmition to the Emperor now uses newly filmed Ian McD, new dialog lines that better explain/conform to 6 movie arc, with Emperor's theme music que added.
- Hayden headswapped in Force Ghosts scene. Apparently not in the unmasking, though.
- Naboo added to end celebration montage.
Those seem to be the confirmed alterations that are majorly noticable. There's more rumors though with more sources than the "fanboy" wishlist that started a lot of the bogus rumors:
- Added shots to the Battle of Hoth to expand scope.
- Alteration/deletion of lines from Luke and Leia's dialog about her mother and what she remembers. Again for consistency with PT.
- Boba Fett's lines ADR'ed by Tem Morrisson. (But not Stormtroopers). This will be the new "Luke Scream" amongst us fanboys, for sure.
A French version of the OT DVD trailer appeared online from a DVD magazine rip last week that included updated shots, including the lightsaber effects, but also offered a couple hints that made some attendees of the LFL press event hint that similar smalls adustments are made throughout the movies. Here are the comparison shots:
Corridor set has new digital extension removing the white light at the end.
This sparked a lot of comments and small observances, like the muzzle flashes on guns in ANH being removed, digital set extensions, matte painting replacements; things like that are the new speculation topic. The French trailer also indicates that the movies have new color timing, removing the blue-ish hue that plagued the SE's transfer.
One last area that gets overlooks in the audio. No one knows yet what has been changed, but all are assuming there will be a glut of controversy, as the sound designers have done complete remixes, going all the way down to the FX stems. We may get some corrections to missing dialog like "you're lucky you don't taste good" and other hated things like Luke's wussy scream as he plummets from Bespin may still be there in all their glory.
We should get a good shot in the arm of tidbits once ComiCon gets rolling, but I'm expecting the full onslaught of alterations to start hitting when screeners land in mid-August.