The only problem with the game is the two player mode. Player one has complete control over their character in both moving and shooting. For player 2, you just get another cross hair, without a character on screen. In a way, it's kinda like player 2 is playing a lightgun game without the worry of being hit.
Putting that minor gripe aside, the game is superb, and truly an asset to the Wii's library. The game is currently exclusive to Japan, but will reportedly be getting a release in North America and Europe during the first quarter of 2010, so be on the lookout for Sin & Punishment 2: Successor To The Sky. It's easily one of the best Wii games out right now, and it's leaps and bounds superior to the original.