I have a few complaints.
This game is fun. I have some problems though. The enemies get too strong for the weapons, and the weapons and power-ups are far too expensive. Granted, I may simply suck at this game, but that doesn't mean that I should have to save up my experience points just so I can buy a better handgun or maybe even a shotgun. Even if I try to save up, I spend it on repairs. This is where Survival Mode shines, but it isn't like you can use the Experience that you gain. That is, unless I just suck at that one too and just haven't killed enough of them. I would like to enter a situation wherein I can use all of the available weapons, but I have not been able to accomplish this.
I only have one other problem; when the ground is covered in remains, it becomes difficult to find anything.
Other than these problems, the game is awesome.