I came across this while researching how to control several stepper/servo motors with the same driver. I would never advocate combining the control scheme in real machining motion control, instead go with one driver unit per axis. However, this is a very clever way to control 4 RC servo-motors. Pricipia Lab's "dissertation" on motor control is a great place to begin with both motion control and Arduino.
Here is the code needed to mover servo #1, 180 degrees.
servo.move(1,180)
At lease from a very high level view of programming. The tutorial goes a bit deeper in the control principles. Adding other features is also cover, such as a joystick. And the best part, they are providing all the code. So check it out here : http://principialabs.com/arduino-python-4-axis-servo-control/
If you do not care to read more about their project, here is a bullet point I thought was handy. They provided a link to get started in Python, the main programming language used on many Arduino boards. See here : http://wiki.python.org/moin/BeginnersGuide
Eavesdropper