These small things show why Nintendo is where it is today. Very subtle decisions which improve the gameplay experience a lot.
This is similar to the momentum in Super Mario Bros. A simple idea and yet it made the game much more playable compared to other platformers at the time.
I am currently writing an iPhone game where the user must move objects around on the screen by dragging them with their finger. The problem is with my game, and just about all iPhone games, is this isn't as smooth as one would expect. Your finger gets caught up in the friction of the screen often, and often the screen doesn't recognize your finger at all.
I am experimenting with ways to fix this, most notably giving the objects a tad bit of momentum such that they slide just a tad after the user is done moving them, making them more likely to go where the user actually had in mind.
This is similar to the momentum in Super Mario Bros. A simple idea and yet it made the game much more playable compared to other platformers at the time.