i think that it will be a great addition to the wii. if the controls are laid down correctly, it will be able to bring a pretty good light gun experience. many of you probably have seen videos of people playing it and using the wiimote B button as the trigger and are not interested in it because of the fact that a guns trigger is not at the front of the gun.
well, in the game Ghost Squad, they have an option to change the trigger button to a button on the nunchuck which will be a lot better. they also have a demo on gamespot that show off the game and the wii zapper.