Interesting story that follows the classic "Heart of Darkness" (or Apocalypse Now) narrative, but suffers from fundamental gameplay flaws
Guns all basically feel the same, with the only difference being the "secondary" mode...usually a silencer, scope, or grenade launcher. Enemies lack variety (really only 5 enemy types...basic soldiers, "maniacs" that attack you with a knife, snipers, elite soldiers, and "heavies"). Some gameplay elements are innovative, like the use of sand piled behind weak glass to wipe out a large number of enemies.
Squad play (single player) is a little frustrating because your team will not move to take out an enemy that you want them to target...if they're behind a wall, they'll just shoot at the pillar until he moves out from cover instead of taking 2 steps to the side to get a better angle.
The cover system isn't the best, and it can be frustrating to try to remain in cover while moving, or run away from cover when an enemy lobs in a grenade.
Overall, worth the play through for the story, but don't expect any huge innovations in the 3rd person shooter genre.