So, here's my observation on the new cantina edit: it's better than the last one? Them firing at almost the same time. But taking the idea that "MACLUNKEY" is a Huttese threat (witnessed in Episode I), the extra dialogue was added to give a *reason* for Han to pull the trigger.
I think Lucas's motivation for tinkering was that he didn't like the backlash to the previous edit but he still wanted Han to have clean hands. What's supposed to be happening is that Han is responding to Greedo being about to pull the trigger, even if he doesn't wait for it.
I suspect that if Lucas had seen this cut through to the release himself, the subtitled dialogue would have been updated, too, in a way that makes it clear.
I think if it had been like this from the get-go it would have been fine, but the fact that he couldn't leave the scene alone is not great, and his desire to mold Han into a less morally ambiguous figure detracts from the character.
