The best shipping plugin would be a combination checking for postal code and weight, although users would be forced to make some manipulation to find out the national rates by weight for postal code prefixes, at least they could be accurate when quoting and calculating the base shipping cost per Postal code. In Canada its a 6 characters alpha numeric code the first 3 characters determine the Province and area in which the package is to be sent. And from that there are online charts that can be used to generate the correct value to be calculated by the plugin. It would be a god send.
