Additional changes made for 4K, according to Bill Hunt at the Digital Bits:
The iconic Fox “fanfare” music has been restored to all of the films (it was removed on some Digital releases). The Fox logo used is the new one (not the vintage one from 1977, 80, and 83), but at least now it’s consistent. And hearing that music again before the start of each of these films is encouraging.
One (and possibly more) sky replacements have been done to the scenes in which the droids arrive on Tatooine. They’re subtle and actually make the scene more consistent, so aren’t especially objectionable.
Some of the SE effects have been tweaked again or redone, for example the shot in which R2 is hiding behind the rocks from the Sand People. The rock positioning has been adjusted and the lighting on R2 has been tweaked to at least make the shot look a little more natural. The SE change is still objectionable, but at least it looks better now.
Lightsaber blades have been tweaked all through the films so they’re now more consistent looking, accurate, and stable. And they are now the correct color consistently—a significant improvement to my thinking.
I also believe that there’s been additional effort to clean up matte boxes and lines, especially in The Empire Strikes Back and Return of the Jedi. Again, this is appreciated and an improvement.
Unfortunately, as you may have heard by now, there’s been another change to the Han/Greedo scene. And it’s even more jarring than before. After Han says his iconic line, “Yes, I’ll bet you have,” the film now cuts back to a quick shot of Greedo again, who mutters an additional bit of Rodian dialogue (non-subtitled), before they both shoot at once, Han’s head weirdly shifts to one side, and Greedo falls.
The sequence in Jedi when the Rebels arrive on Endor—which on Blu-ray was oddly blurry (likely caused by some kind of registration error in the film scan)—has finally been fixed.