Let's Make Robots!

Arduino IO Expansion Shield v5, only for servos ?

I just got the v5 IO shield, and I'm going to put it on my Uno R3. (actually bought this by mistake, what i was really thinking about was the Port expansion shield).

I am only using two servos for my project, and these fit just fine. these i put on port 10 an 13.

What I am currently wondering is if the rest of the digital ports can be used as before or does it have to be servos or other parts that has the same 3-pin female layout (Signal-Power-GND).

The rest of the digital ports on the Uno are used by my Dagu motor controller (which is powered separately), a sonar and an IR eye, 

My question is this:

Can i use the rest of the digital ports as usual (obviously i have to use female cables instead of male), while an external power supply is powering just the two servos ? (using the screw connector)

Or is the external power going to interfere with whatever i connect to the Digital signal pins (not using power and GND)