In ANH, the Greedo scene has been tightened. From leaked footage, Greedo now shoots exactly 2 FRAMES before Han does. That's less than 1/10th of a second at 24 frames per second. Also, in both the SE and the DVD Han shoots Greedo TWICE. Also, the DVD restores Han's, "Yes, I bet you have," as it sounded pre-SE.
Jabba's appearance in ANH has been redone from scratch and screenshots from the SE are no more representative of the DVD than pictures of the Irish actor who was on the set. Jabba looks a LOT better on the DVD, better than his appearance in Episode I.
Also, the DVD of ESB removes the scream added when Luke jumps after the duel, and actually FIXES flaws in the original like in the shot on the Executor bridge that is obviously flipped backwards, the officers uniforms have been digitally corrected so they appear to be turned around correctly. That is an indisputable improvement.
Finally, the incredible work done restoring the sharpness and detail of the film and recompositing original effects will make the blending of digital effects into the movie appear far more seamless. When you actually watch the films you will feel the story being told more intensely than before simply because you can see so much more detail and it seems so much more real.
Experience the films as they are now. Hear the story in your mind based on what you see and hear, not on what you remember. Feel, don't think.