One of the biggest hurdles facing piano players is getting their pinky and ring-fingers to cooperate with other fingers on the piano. Think about it - the thumb, index and middle fingers are quite athletic, but when it comes to moving quickly, the pinky and the ring finger are always struggling to catch up.
What's a piano player to do?
Historically, piano teachers have had students practice repetitive musical exercises faster and faster, for longer periods of time. While this strengthens the fingers on the keys, it also has the negative effect of developing a "robotic" like quality on the piano. In addition, practicing strenuous finger exercises that remain "locked" in one hand position for a long period of time have the tendency cause injury. Yikes!
The answer to finger dexterity is to spend time playing musical exercises that include many different horizontal finger movements throughout the exercise.