In reply to Stone Muppet: depends on your goals, to get better and campusing on the board learning the 'swing' like you mentioned will help, but will slow strength development.
If you watch advanced climbers use the boards they mainly keep the lower half of the body controlled, feet together to work the back/forearms and fingers.
I know when it comes to real climbing your using your body and momentum in any way to send the boulder or whatever your doing, but when it comes to using a training tool, i personally do it strict as i can to focus on the #1 point, strength gain.