I just wanted to let you know that there is one important step missing from your Installation instructions. After installing the plugin, you have to go to Appearance -> Widgets and drag the widget you wish to use into the newly created "Arbitrary" section. Then it spits out the elusive widget ID and shortcode that can be placed anywhere.
Had to stumble around a bit before I figured it out and wanted to save some other people a little trouble. Thanks for the widget!