The problem lies not in the individual components - each of which, taken on their own, are enjoyable - but in the composition of the whole. Different gameplay elements actively undermine each other. While the new Nano Forge powers, which range from damage buffs to AOE attacks, are fun, ammunition is so plentiful that conserving it is never an issue, meaning the player can use the (usually more versatile and effective) weapons without restraint, negating the need for the Forge. For the same reason, ammunition limits on weapons mean little; you may as well continuously use the weapon with which you can kill the fastest. This takes away any meaningful choice in weapon selection and use - I completed much of the game using only the assault rifle and charge (grenade) launcher, switching to other weapons for no reason other than because I was bored of my present loadout.
Most egregious, however, is the way the aliens invalidate any meaningful use of the Geo-Mod technology. Sure, you can blow up a bridge, but why would you? The aliens will simply pounce across; the only person inconvenienced by the loss of the bridge is you. You can knock a tower on its side, splitting the enemy forces in half, but what good is that when the aliens will simply leap or crawl over the rubble without effort? How you choose to attack has no real meaning; no matter what you do, aliens will converge on you from all angles. The only reason to destroy buildings is to collect the salvage points they leave behind, which is a cheap and artificial way of getting the players to use the technology - it adds no depth and would be effectively the same game without destructible buildings, except you'd spend less time running around already-cleared levels, blowing up everything in sight to collect their treasures.
Likewise, the game advises you to use your Nano Forge to rebuild cover during a firefight, but why bother? The only time you need cover that desperately is when you're either surrounded, making cover useless, or when you're being attacked by a weapon large enough to destroy your cover immediately after rebuilding it. Besides, dodging is an easier way to avoid harm long enough to regenerate your health fully. You're occasionally required to use the Forge for one of two purposes: either to rebuild a plot device, which is functionally identical to pulling a lever (hold down the correct button for a moment and the object is rebuilt), or to rebuild destroyed (either by design or by you) structures needed to continue, such as a bridge or walkway, which adds nothing to the game except requiring you to hold down the rebuild button while moving. It's a shame the technology is wasted this way, because puzzles involving the Forge could have been both interesting and a nice break from the constant gunfire of the rest of the game.
What's left is a game almost without decisions. It doesn't really matter if you destroy the buildings, it doesn't really matter what weapon you choose to use, and it doesn't really matter how you approach the encounters. The only thing that does matter is your ability to aim and dodge.
But you know what? Those parts are actually pretty good. Combat feels right. and there is a sensation of impact when your hammer makes contact with an alien's torso or your boot comes smashing down on a bug; better still is punching one with the L.E.O.'s mechanically augmented fist, causing the creature to outright explode in a shower of gore. Each gun is distinct and fun to use (though not all are equal in power), the aiming feels right, and the enemies die easily enough to impart a satisfying sense of power to the player while being numerous enough to occasionally be dangerous.
Red Faction: Armageddon is not a bad game; it's simply a confused game. At its core is a solid (if simplistic) third-person reflex shooter, and a good one, too. The problem is that everything about the game undermines its primary selling point, the Geo-Mod destruction, leaving behind a product that fails to reach even a fraction of its potential.
Bottom Line: Red Faction: Armageddon is a polished and satisfying reflex shooter that removes meaningful decisions from the game and trivializes its own greatest technology.
Recommendation: If you like the challenge of rapid aiming and dodging, you could do a lot worse than Armageddon, but if you like using destruction creatively to solve problems, you should look elsewhere.
This review is based on the Xbox 360 version.