@mildmolasses: Oh, I don't deny it's fun. I actually enjoyed myself immensely, I would dare say that I had more fun than in Uncharted 2, since TR's enemies are not bullet sponges. I'm just sad that the game tries to tackle a theme it's ultimately uninterested in pursuing.
@tangoup: You have to have the weapon equipped, I think. Also, to perform those other skill-unlocked takedowns, you need to actually go to aiming mode and press the attack button. Unless you're referring to something else.