I’m not sure if you can change the widget title to an h1. I think it’s possible, but you would have to add some code/php filter to make the change. Although you could just manually add it in if you’re already using a text widget. That’s exactly how they did it in a couple places on the demo.
<h1>Title goes here</h1>
and if you want to add a class to it you can <h1 class="widgettitle">Title goes here</h1>
Does that help?