The gameplay is simple, but fun. They need to be used to end a mission sucessfully. The addition of underwater weapons is awesome, although they are rarely used in singleplayer missions. It is easy and simple to target bad guys, and to take them out with a burst of fire. Some pitfalls here, though, is the fact that the weapons aren't balanced.
Some guns are just obviously better than others.
You'll find in missions, that, no matter the objective, you keep using the same, or just a couple setups over and over with little change. The HK G11, and the AUG are the tops when you look at rifles, plain and simple. The OICW, supposively the focal point of the game, and its name, downright sucks in a shootout, because it can't fire full auto, and therefore can't keep up with the fast paced action. That brings me to the enemies. While their AI has been mproved, they still follow highly regimented battle plans, and you can usually kill them with ease.