The Plot: While basic story is interesting, there are parts of the plot that feel hastily put together. Almost like the designers forgot about the story for most of the game and then remembered it at the last second.
There are also a few places where there is no explanation of how you got from point A to point B, you just appear at point B. All in all, the basic concept was fun but the focus of the game was clearly the first person shooter aspect.
The Gameplay: This part of the game was incredibly well developed. At the onset of the game, I was worried that it would get terribly repetitive and boring. Because there are a number of ways to accomplish optional objects however, it never got to that point.
The skill system allows for additional abilities as you progress through the game. The number of experience points required to get a new skill stays static, so while not a true leveling system it still allows you to somewhat customize your character (though by the end of the game it is possible to have every skill).
Like all first person shooters, there are points that can get frustrating (even playing on the easiest difficulty). And the ability to unlock weapons for free by accomplishing optional objectives instead of buying them was fun.
All in all, fun game that is definitely worth a play through.