Loving the plugin.
Two suggestions based on your latest upload.
Having a title as an option is nice, but if the site chooses to not have one, you're currently rendering an empty
div, which leaves some awkward looking whitespace. It might be no harm to check the inputted title before rendering?
This is what I've hacked in - https://gist.github.com/4142002.
Also, and this could just be my theme, but your
$before_widget at the very start of widget.php is doing this crazy nested widget thing. Removing that echo statement seems to clear it, but just thought I'd give you a heads up.