Probably the coolest, technically speaking, portion of the new comments is the manner in which most of the page is created. No longer do we create static HTML in PHP and send you a huge HTML page. Instead we give you the basics and, via AJAX/JSON, we make requests to the API and dynamically create the DOM using the FlyDOM jQuery plugin. The FlyDOM JSON templates are a stroke of genius if you’re looking at loading JSON dynamically into the DOM. The advantage of this is that initial page loads are much snappier and you can load the threads you wish to read on demand.
Daniel has written up a detailed overview of the design decisions so if you’re interested in the design aspects you’ll definitely want to check that out.