Man, I have to say that I am really regretting picking this game up.
After already having played Orcs Must Die 1+2 and Toy Soldiers, I was incredibly excited for this game. I am a huge fan behind the concept of these games. Merging action gameplay with a tower defense strategy element is one of my favorite genre combos. It fixes the boredom of just placing traps, and it forces you to think more than your typical action game. So far the single player in Iron Brigade is the worst out of all of this type of game I've played (at least in terms of single player).
a. You only get to choose a maximum of different 4 weapon emplacements (traps) per level and that's only if you choose the weakest Mech with the least amount of fire power. To make this worse you are limited even more by only being allowed to bring a limited amount of categories of traps with you ON TOP OF THAT! Don't have a slot to carry a mortar/heavy weapon emplacement? Too bad, choose a mech that does.
b. Having to manually collect the scrap (money to spend on traps) is a hassle even with the magnet to suck them toward you (there is a special trap that sucks them in for you, but that takes up one of your few slots). The scrap itself are actually physical objects that explode from enemies and can become stuck behind buildings or drop into pits. Worse still, they disappear after a short amount of time meaning you need to be at two places at once to get it all (almost like it was made with co-op as the focus, hmm).
c. You get so little scrap every wave that I rarely feel like I'm able to cover all the spots I want too. Another obvious clue the game designed around co-op is that there are usually 4 or so points where the enemy will spawn from. Having more than one person would be invaluable for covering all the sides of the maps and collect all the scrap. In single player I always feel like I'm getting swamped and I don't know where enemies will come next so I might put traps on one route only to have another route start spouting enemies. Not to mention the multiple enemy types that actively destroy your emplacements, which is bullcrap and not easy to defend against (unless you have the perfect combo of traps and lots of scrap to buy them all with)
d. At first I liked the idea of the games loot system, but the more I've played the less I'm liking it. I feel like my current weapons and traps are all far too weak and if they were more powerful I'd be having more fun. A good loot system makes sure that you're enjoying yourself with you current weapons which makes finding better weapons even better. In this game all I feel is relief when I get a gun or trap that doesn't suck as bad.
e. I only had this problem on the last map I played, but halfway through a mission I had to start defending a different objective (a big cannon) and for some reason my machine gun traps would not shoot at the enemies. They just sat there and did nothing. I was probably a bug, but it was one that failed the mission for me and made me not want to play the game again.
So yeah, overall I am very disappointed with Iron Brigade so far. Hopefully with better loot (like a medium mech chassis that lets me bring a support, light, and heavy gun) I'll start enjoying the game a bit better, but I don't think it will fix a lot of the issues I've had with this game so far. Compared to OMD!1+2, and Toy Soldiers this game just doesn't feel like it was built well for a single player experience.