Awesome game, but fix the save bug!
For the most part, this game kicks ass. I spent a good 3-4 hours this morning playing it. The multiple different pieces of equipment and soldier classes lend a great deal of the tactical element to the game, which I enjoyed a lot. The fact that different enemies have their own health statuses, armor classes, and weapons also causes you to think ahead and determine which target is of the highest priority. Constantly upgrading your equipment gives an experience that is often tricky, but not unfair.
Sound is good, music is good for the most part (the music club beat grated on me a little bit, but since you said this is all copyright-free, you have a limited selection), and the art captures the true Madness style.
Now for the bad:
The 2.5-D approach works well for the most part, but often times an enemy or another soldier will get in the way of clicking on a space I want one of my team members to move to. This occasionally causes me to shoot an enemy I didn't want to, or makes it nearly impossible to get my squad into an advantageous position.
The most frustrating part of all is the save bug. I believe it has to do something with switching primary and secondary weapons. Sometimes when I save my progress, my character(s) will be outfitted with weapons they were not using previously. This is annoying, but permissible. What caused me to quit playing altogether is the bug in which a squad member's equipment is replaced by zombie hands. This bug ERASES the weapons the soldier was currently using. After the Heavy Machine Gun was destroyed this way, I gave up.
This bug can be corrected if you pay attention to your characters' weapons after you save--change their weapons around and it should usually be resolved. However, if you don't catch it, you can ruin your progress.
It's a shame, because I really enjoyed this game up until that point. Next time, try to playtest a little more thoroughly. Other than this issue, Madness Retaliation was a thoroughly enjoyable experience.