Yeah, hearing your "sword" clang in your hand when fighting in Red Steel, or hearing your arrow "enter" the screen in Zelda is pretty nifty, and actually really cool. However, for some reason, I think they have a few other things to talk about.
They also revealed that the system will always be on, like sleep mode for the DS, when you're not playing. This allows updates to your game to download even when you're asleep.