I can't put this game down. I've never played an FPS that has been this crazy, this intense and this free. Far Cry was good for that, but it doesn't match the craziness this game has. I won't spoil any of it, but this isn't a game where hiding in the jungle is always an option, sometimes you're exposed, out numbered and have to rely strictly on raw firepower to reduce their numbers.
I also like that although the game is extremely sci-fi, you're not immortal by any stretch of the imagination. Dying isn't uncommon. I also like that the damage taken as opposed to the damage given isn't so unbalanced. Even though the enemy doesn't have nanosuits (kind of...

), they're still wearing armor and placing your shots carefully is essential to staying alive. Although the torso is a big target, it's also heavily shielded.
All in all, I think this game is one of the best FPS's in years.