There is a lot to the region that the WHS includes - it's easy to spend weeks here if you really wanted. I loved spending some time based in El Chalten and hiking around Mount Fitzroy, for instance
But I think the highlight is the Perito Moreno Glacier - one of the most popular tourist stops in southern Patagonia. Busloads of people come in and out of the site every day and it’s one of the main reasons travellers bother to stop in the nearby town of El Calafate (although it is actually quite a nice place in its own right). In fact, the whole region seems to be going through a tourist boom at the moment and visitor numbers are definitely on the rise.