The Good: Good voice acting, lots of weapons, decent fun with another player...
The Bad: A complete nightmare without one, looks bad, repetitive, boring, and just bad
There was a good reason why I avoided the original Army of Two and this was because of the terrible single player AI. The game was only fun with another person, but even then it was flawed. The 40th Day tries to improve this, but it failed. You would normally expect the console experience on the PSP but all we get is a top down clear-the-room type game.
The story is even retarded in a sense that it doesn't make any sense. You are in China during a mission and something goes wrong and you have to escape. Why not just call for air support? I don't know the game never explains. At first the game is pretty fun with its fast paced game play. You can switch between a primary and secondary weapon (assault rifle and shotgun) which you have to use in different situations. You have a melee attack and you can command Rios to hold or go into Aggro mode. This is supposed to make him more aggressive, but all it does is piss you off. You can duck behind cover (but you can still get shot most of the time) and upgrade your weapons as well as buy new ones. If Rios ever goes down you can revive him, but if you die before you get to him its game over and vise versa.
So what makes the game not fun? Too much in fact. First off the AI is absolutely dumb. Once the screen moves to a new area you can't go back, but some times Rios will still be back there and he's stuck for good. If you die and need him to revive you you're screwed. A lot of the time Rios will just charge out at enemies and get his health depleted quickly. This is especially annoying during boss fights. There are also a few glitches where you will get stuck in objects which can be very frustrating. Upgrading weapons takes forever since you can't accumulate cash fast enough. By the time I got 2/3 through the game (and I stopped there by the way because the game just became unbearable) I only bought two guns and upgraded my first two. The only other things you can do is press buttons and hack turrets to use against the enemy. The game just isn't exciting anymore after the first level.
Does the game at least look good? Kind of is your answer. Some of the environments looks OK, but everything just looks too cartoony. The game sounds OK and it has good voice acting, but it can't save this piece of garbage. Does co-op save it? More so yes. If you have a buddy the game can be quite enjoyable, but the redunant game play makes it a bore fest very quickly. The awesome bro-li-ness of the console games doesn't come across here and this makes the game a flop.