[Skunkworks] Number Portability

Is number portability real worth it? The process of changing networks and the cost,would I rather just buy a new line from the other network for 20bob on the street?ama? I dont know much about number portability (excuse me if my question is laymanish..),i would appreciate a small lesson from a SME on this list especially the advantages from a customer point of view and the economics behind it from a network point of view.I would not mind the technical aspect as well (though not so deep). Thanks