I can agree with you on the pacing of the game, it's way too slow to start with and going through the levels is like zzzz. About 4-5 chapters in, the game started to pick up and me and my brother started to enjoy it more.Not sure if i'll be going back to it once it's complete.
Still they could have made it a non light gun game.
Overkill is the better light gun game, but it suffers from slowdown at times which is annoying. Not like it's pushing the wii