Dirty Interface, But Works

It does what it says it should do, logs you in and optionally redirects you.
Works in both page and widget.

The biggest problem is the odd bold, “Login” that the shortcode includes in the page, centered mind you, that is not needed. Unless you center the shortcode, the words are 2″ away from the form.

I edited the plugin to remove this, but my suggestion is to remove it from the shortcode, let the user add their own style and format above and below it.

In addition, you appear to be forcing the form to align left, and not allowing the user to control page location.