I'm curious, so if (when?) California ends up successfully hunting down some criminals with this, what is your new position going to be? They were going to get caught anyway, or something like that?
Legitimate gun users will, at best, use their weapon in self defense, in which case they'll be sitting there waiting when the police arrive, so no need for microstamping.
The "crime of passion" so popular in TV shows are few and far between, and there's usually a huge amount of other evidence.