Sweet, but...
This was kind of missing a couple of things. The very first one that bugged me was the lack of decent death animations for the enemies. If I don't see that little bug things explode and leave a giant mess, then what was the point of shooting? Another is more diverse/larger environments (but I understand if you were trying to keep the file size down).
The voice acting was funny (in a good way) and the sounds and everything else seemed alright. Just make the violence a bit more graphic and try to make the maps seem less planar.