(didn't read all those other posts)
I thought that the clones didn't have second thoughts. I thought order 66 was wired in their brains. They're engineered soldiers, and thought they might have feeling, friends, etc., when orders wired in their brains kick in everything disappears and the orders become main priority.
the Clone Wars tv show thing (recent) sorta implies that they might've had second thought, but as shown in ROTS, not one hesitated.