If I had to use a metaphor to define this game, it would be "Double edged sword". Or maybe "Golden garbage"? Whatever, it has big positive points AND very negative points.
The plusses are obvious: Nice story, fun gameplay and excellent sound effects and, to some extent, graphical effects.
The negatives are: Lack of enemy diversity/specialization - they basically make a beeline for the player, and the hidey one tends to stay put even after taking bullets. Weapons are also basically the same overall, only the shotgun and CL are really different (vulcan is absurdly underpowered).
Controls are bad, simply put. Why not reload with "R"? No hotkeys for weapons either? What the hell?
The "break" point (and what makes this game rate low) is the final medal req (all challenges completed) because it "forces" the player to play the swarm and story mode so many many times and kill so many many many enemies. This makes the game get old really fast. 5 waves for a round, 3 rounds for a set etc. is an absurd and will require many days to complete. so, in short, FAIL.
I hope the sequel is better, since you seem to pay attention to feedback.