1. I think if there is a fatal shooting it shouldn't be up to the police to decide if it was "stand your ground." I think it must be reviewed by the DA to see if there are grounds for a trial, and if there is uncertainty, a jury (or judge) should decide.
2. I think stand your ground is only going to be stupid and dangerous; that's my bias. It seems unnecessary, given that self defense is already justified. Maybe I'm ok with wording of law that mentions a "right not to retreat" in the context of your home, but not in public.
3. This is a dangerous road to go down. Especially with conceal carry/open carry. For example, what if both of the people in Florida had a gun? What if the shopper saw this guy yelling at his wife, had a "reasonable threat for her safety," and shot and killed the eventual shooter first? Essentially, this law is leading to a situation of "if you are going to initiate physical contact, might as well just shoot them right off the bat, because what if they are carrying a gun and will shoot me if i push them." And then people will say "oh, but you shouldn't escalate to violence from words" but, honestly, are pretty fine with, for example, police escalating to brutality when it is "just words." What if the case had unfolded just the way it did, but the shooter fired 2 shots and killed a passerby? Florida would just be like "oh well, thoughts and prayers, guy was standing his ground." Going back to the "when to start physical contact" question, lets say it's an open carry situation, and a guy wearing a gun starts yelling at you aggressively for stuff that's not his business...that seems pretty "reasonably threatening"...does that justify yanking out a gun and shooting before this person yelling and wearing a gun escalates things?
4. There is no way to talk about this and leaving race/gender out of it. I don't think this law is ever going to be equally applied, which makes it really troublesome. The way it is always worded in the press is "reasonable concern of death or injury," which is already used to justify tons of police brutality, by pushing the edge of "reasonable" in front of a jury. So, its just going to play into racial stereotypes in terms of "isn't it 'reasonable' to be scared of that black guy?" kind of stuff. I would make a healthy wager that stand your ground is going to be very disproportionately applied.