Show customer group in order e-mail (for redbeetstudio)

Problem: Show customer group in order e-mail.
http://www.magentocommerce.com/boards/viewthread/71736/

Possible solution
In order for this to work in the e-mail template:

{{var order.getCustomerGroupName()}}

you have to create a method in the Order model (overwrite it or edit the core at your own risk).

function getCustomerGroupName(){
$group = Mage::getModel('customer/customer_group')->load($this->getCustomerGroupId());
if ($group->getId()){
return $group->getName();
}
return '';//or any default value if the customer is not in a group or is a guest
}