Struggles with pages (used as a placeholder for confirmation messages in Ajax version). Basically the page you first use gets stuck in its memory. Changing pages really messes it up. And the echoed shortcode embedded in themes won't go to the same page as the widget version (I use both in my theme).
Apart from that, and the br element inserted between the label and the input (what a pain! can't style that too easily)works very nicely.