I hate to pile this on another comment, but I'm not sure how to start a new message to you here....
Your subscribe form is missing some kind of closing tag (because if it is not the last widget in the column then the title of the next widget bleeds into the subscription form). I'd say it was the template, except your widget is the only one exhibiting the behavior.
But what I really really need is to use the widget real estate efficiently.
That means a SMALL form on the widget with only:
Title of widget
Email: [ ] (go)
This mini form could post to a PAGE with the full form that includes First Name, Last Name, Email (already filled in) and all the disclaimers and other goodness like reasons to subscribe, custom fields (ie daily vs weekly updates, etc etc etc.)
Would it be possible to get the secret sauce for building my own subscription form that posts to your plugin for the heavy lifting?