Here is one thing that I have noticed with these macro's.
After you do the /script SetBinding macro, I can auto loot with that button.
Lets say I set the button to 'g'. When I push 'g' to target a person it will loot that person. And if you it enabled such that you auto-loot without having to push shift, it will pick up the loot on the selected mob. However, maybe this is strict to my machine only because when I use the macro to grab quests and such, my mouse jumps over to the second monitor and i locate the person I want to select by moving my mouse around that monitor without deselecting my mains WoW window. Weird how the macro does this but it has made looting in WotLK so much easier...