Interesting concept, but flawed game. It's not that is bad or anything. It's fun, but it could have been so much more than it is. The things that made this game "fail":
1-It tried to fit itself within the fads of it's time (AKA feel like a Gears of War knock-off) rather than try to have it's own thing.
2-The upgrade and weapon marketing system it's just there to make you look for bonus items and money, making the campaign a bit longer (hint: play the game only using the single handed guns, it plays waaay better)
3-Fighting the soldiers is more interesting than fighting the mutants, but in most of the time, you fight the mutants.
4-The campaing was too short (especially if you ignore the bonus hunting).
5-The story is a mess of events and characthers that you don't see.
But, I still recommend it: tons o' fun, each single handed weapon (the pistol, the sub-machinegun, the revolver and the sawed-off shotgun) complety changes the way you aproach a level, and at many times, you'll feel like a boss when completing a mission. In short: this game coulda been awesome, but it's just... good.