Pros: Very fun. Co-op based. Great graphics.
Cons: Campaign is short. EA servers are weak. Audio is weak at times.
The bottom line: This is a great game, if you have someone to play it with. It is fun by yourself, but not nearly as fun playing with a real partner. Very addicting.
Welcome to the private sector, where war is your business and business is good. Join the SCC, the worlds most elite PMC, and help Rios and Salem fight enemies of freedom while still making a healthy profit. Borrowed from http://www.ea.com/armyoftwo/home.jsp

Army of Two is an EA co-op based, third person shooter. You follow Rios and Salem as they complete missions founded by the SCC, a private military organization.

Story - *General, but may have spoilers*
Salem and Rios start out as US Army Rangers. You fly into Somalia for your training and first mission,take out your first target. While in Somalia, you meet up with a SCC soldier, name Phillip Clyde. He gives you the scoop on your targets location. After you complete the mission, you are recruited by SCC, with the major selling point being the amount of cash that could be earned.
After Somalia, you are now working for the SCC in the remainder of the missions. These missions include Iraq, an aircraft carrier, China, Afghanistan, and Miami. Through out the missions you learn who you're really working for, and you're never sure who to trust.

Graphics -
The details and graphics in the game are very sharp. There are a couple places that it seems the developer may have slacked, but those are few and far between. Everything around you, in the game, is absolutely amazing, from the menus to the game play. AO2 has plenty of cut scenes as well, to help keep your eyeballs very stimulated

Audio -
I am not taking full advantage with the audio (no surround sound), but it sounds decent coming out of my regular TV speakers. You hear voices in the background yelling out commands, as well as tons of gunfire. However, a lot of the gun fire sounds a little bland. It seems most guns sound similar, which is not a huge deal to me, but I have heard complaints of it.

Game play -
The game play is smooth. The motions you and others make all appear to be very realistic. There are a lot of parts that require your partners help (which I will discuss later) that breaks up the fluidity a bit, but it is worked in nicely. The controls are easy to learn as well. It is very easy to change weapons, take cover, and roll/slide to safety.

Army of Two has 3 levels of difficulty. They are Recruit, Contractor, and Professional. If you play recruit, and you are used to playing shooter games, you will have no problem running and gunning, while doing everything yourself. On contractor, you will have to rely on your partner a little more. You start to use your aggro more to help you flank the enemies. On professional, you need your partner with you the entire time. You die quicker, and enemies can take a few more bullets. Great communication, and use of aggro will help you advance through professional levels. You unlock the professional level after you complete every mission on contractor.

Co-op Maneuver List
Step Jump: Used to reach higher places. One person crouches down, and lifts the other up, while the person on top then reaches down and helps him up.
Back to Back: Straight forward. The players put their backs together and spin 360 degrees, killing enemies in all locations. You never have to reload during back to back, and you do not use your ammo.
Driving: The only SP player vehicle is the hovercraft. One player will drive, while the other mans the gun.
Kudos: You can congratulate your partner, or smack him at anytime. This is more for fun, and plays no big role in the game.
Healing: You do not die instantly. You first get wounded, which your partner has a chance to drag you to safety and heal you. While a player is getting drug, both players can still shoot at oncoming enemies.
Aggro Meter: The more you shoot, the more you are seen (you glow red). You can fire a lot, to allow your partner to flank undetected. While your partner is glowing red, you become transparent and harder to see.
Feign Death: If you are near death, you can "play dead". You will lay on the ground, while the enemies will go for your partner. Once the cost is clear, you can get up and attack or find cover. While you are feigning death, your partners aggro builds up.
Co-op Snipe: Both players get into a sniping maneuver to double their power or take out two targets at the same time.
Weapon Swap: You can switch guns with your partner at anytime.

Also, if you don't have a buddy to complete the campaign with, you can play with an AI partner. You control his every move. You can have him hold, advance, and follow. With each of these, you can have your partner do them passively or aggressively. This will determine the aggro you or your partner will have.

Controls
Army of Two controls are a little different than other games, but easy to learn. Here is the list:

Right Trigger: Fire weapon (slap partner when close)
Left Trigger: Precision Aiming
A: Action button, high five partner
B: Cancel actions
X: Reload
Y: Slide towards cover, roll, climb
Back: Activate GPS
Start: Pause game
Left Stick: Move, click to crouch
Right Stick: Aim
Left Bumper + Up D-pad: Primary Weapon
Left Bumper + Right D-pad: Special Weapon
Left Bumper + Down D-pad: Grenade
Left Bumper + Left D-pad: Secondary Weapon
Right Bumper + Left D-pad: Co-op Snipe
Right Bumper + Right D-pad: Swap weapons
Up D-pad: 1x for Passive advance, 2x for aggressive
Right D-pad: 1x for passive hold, 2x for aggressive
Down D-pad: Activate cross-com (see what partner sees)
Left D-pad: 1x for passive follow, 2x for aggressive

Weapons -
AO2 has a slew of weapons to choose from. You have 3 main categories; Primary, Secondary and Special. In the primary you will find your assault rifles, light machine guns, and shotguns. In secondary you have your handguns and sub-machine guns. Special is full of sniper rifles and RPG's. Each weapon has it's own upgrades as well. These include stocks, barrels, clips, silencers, and many more. You can also "pimp" each weapon to make it look flashy! Each upgrade costs money, which is earned during the campaign.

Gear -
You can also change your gear. While this is not as extensive as the weapons, it is always fun. You have 3 types of armor; light, medium, and heavy. Also, Salem and Rios have 12 different masks each. You can purchase each mask for a little bit of earned cash.

Multiplayer -
Multiplayer is a good break from the campaign. There are four maps you can choose from, right now. In MP, you work with your partner against two other players. Also in the mix, are tons of AI players trying to stop you as well. As time goes by, you will get an objective ranging from extractions to assassinations. Your goal is to complete the objective before the other team. If you do, you earn money. Which ever pair has more money in the end, wins.

There are minor objective as well in the multiplayer. You can collect these to help boost your cash flow. You also earn money by killing the AI, as well as the other two players. There are weapon depots around the maps. Here you can purchase upgrades or new weapons. This, however, will decrease the money you have earned.

Overall -
Through and through, this is an excellent game. It is very addicting, with or without another player to play with. There are several achievements that help prolong the game, if you're into that. The campaign is shorter than I would have liked, but that does not keep me from playing it over and over again. Also, the EA servers appear to be a little spotty at times. If you are looking for a fun and addicting co-op based game, look no further!