This worked perfectly on my first try. Just follow the directions and you'll be up and going in minutes. Very impressed.
One note. Our constant contact guru just added a new list, that should be the default list for auto-subscribing. An hour later, the plugin doesn't seem to be picking up the new list name. So I'm going to see how else I can find out what it's ID is, because the IDs don't seem to be sequential. Not sure if this is a constant contact issue/or a plugin issue.