Up until now, all of the tweaks and changes that have been made have not really bothered me. Perhaps the whole Han/Greedo thing a little bit, but that change has existed for fourteen years now, so I guess I've just gotten over that one.
And I know it shouldn't bother me, but it does, so I'm just gonna say it...
Lucas has ruined the entire Star Wars Saga for me.
Let me explain.
When, as I kid, I heard rumors of a total of nine Star Wars movies, I was pumped. Then after the PT came out, Lucas was like "no no, the entire movie saga is about Anakin". Okay, I can drink that kool-aid and buy into it. Fine.
Then taking the fact that the entire saga is about Anakin, the lynch-pin moment for me HAS ALWAYS been the moment, where Vader finally has had enough and kills Palpatine. That scene, to me, has always been perfect. The sound of the force lightning, Luke's screams of pain, the delight Palpatine seems to be getting from torturing Luke to death, the score from John Williams which is rising to a crescendo, AND THE F**KING FACT THAT DARTH VADER JUST ACTS WITHOUT SAYING A WORD.
The entire saga, whether it was 9 year old Anakin, 20-year old Jedi Padawan Anakin, 23-year old Jedi Knight Anakin or OT Darth Vader - the character of Anakin/Vader has always been a mouthy "I'm a bad ass and I know it" character. For him to stand their silently reflecting on the tragedy that is his life and to finally take control says all that needs to be said. He does not need to say anything.
Now, keeping in mind of course that these are movies and I can definitely see how Lucas likes to repeat themes and moments. If he wanted to add something there, he should have taken the line from ROTS, right before Anakin stops Mace Windu, he says something like "No, I need him to live", found James Earl Jones, written a variation on that ROTS line like "NO, MY SON MUST LIVE" and have JEJ record that, process it to sound like Vader and insert that into the movie. If that was what was added, I think I would still be upset, but at least it would correlate to something that already existed in the saga. To take the horrible "NOOOOOOO" from the end of ROTS and edit/re-process it and add it here is just adding salt to the wound that was made when he decided to add Vader dialogue into the scene in the first place.
I'm with Phruby - this may be the one minor thing that stops me from buying the saga on BluRay.