Setting the content of nodes to either escaped text (using content), or HTML (using html-content) is pretty obvious. But here's how you can use HTML with the other Enlive transformers.
[:div] (append (html [:script "alert('Hello, World!')"]))
The html function takes a Hiccup style data structure of nodes which it will convert to an Enlive map for the HTML.
(html [:div.control-group [:label.control-label "Label:"]])