Thanks for all the advice. However I would like to point out that the reason I left Arduino was all of the electronics skills that I was unable (perhaps unwilling) to learn. That's why I delved into the EZRobot product instead. But if I could ask one thing, why does a linear solenoid require all this extra circuitry but a rotating servo does not? They both change electrical motion to physical motion. Why is linear motion so much harder to implement than rotational motion (which requires no special circuitry)?

A servo has circuitry built in to handle it. There's a small circuit board inside (believe it or not) along with an inductive motor. Btw linear servos do exist if that's what you're after. Here is a conversion kit for a standard servo. This will give you more precise control than a solenoid however it doesn't have the speed a solenoid has. How will you be using it?

I think solenoids aren't a good choice, they need relative much current if they are active and get hot very fast. I own some pinballmachines and know solenoids, most solenoids in pinballs will only akt for a short time, except the flipper fingers, but there is a little trick....if you press the buttons the fingers have much power because they are activated by the power-coil and switch to a smaller coil that is for holding the finger in position. This trick will be used, because the powercoil would burn when it's activated to long.

You can use linear servos (look at ebay) or use a other relution.

Can you tell more about the projekt? Is it really required that buttons will be pressed, or is it possible to solder some cables to the switches that should be pressed and switch them directly with a transistor or relais?

Marc