@Frode
I use the shield with a Fez Cerbuino Bee. I had to change PWM Channels to other pins of the Cerbuino.
I use the
http://netmftoolbox....ardware.HBridge
Library. It works.
Sometimes i had a strange behaviour, when the voltage drops below 6V. I seperate the VIN from Cerbuino and the Ardumoto shield. Now it is better.
I use a very old version of Ardumoto Shield. The version has the PWM channel on Pin 10 and 11 and direction on Pin 12 and 13.