Very nice article indeed.

One commonly used variant I missed in the article and I'd be interested what it's positive/negative aspects are (if there are differences at all):

    <script>
        var script = document.createElement('script');
        script.src = "http://example.com/awesome-widget.js";
        script.async = true;
        document.getElementsByTagName('head')[0].appendChild(script);
    </script>

(Note the additional async param)