I have wired up my Dagu motor controller to the same switch that gives power to the logic (ie Arduino board) - they are on different circuits though...
The DAGU instructions say to power up the logic first:
"The motor power supply should not be connected without first connecting the +5V for logic."
Is this (ie powering them both at the same time, or the logic slightly delayed - it goes via the Arduino board regulator) going to be a problem? Why does the logic need to be powered first?