The only bad thing I found in this game was the difficulty. It was a fairly easy game and you could beat it one player if you put your mind to it. Other than that, nothing was wrong.
Buy this game. It's one of the greatest shooting games I've ever experienced and you will surely enjoy every minute of it. It's very rare to find, but I'm sure you might get a chance to play it at your local arcade or something, but remember you need to play this game because I am about 99% sure you will like it.