Having seen the vast majority of our external deployments over the years, I have yet to see one (that I know of) which is using the support center as the landing page. I do know some use it, as a resource page within the larger community, but I believe (and this is just personal opinion) that the Support Center most likely doesn't give enough flexibility around overall visual design and navigation to allow for it to act as the central landing point. Obviously plenty of the communities we run aren't only doing support either, but it's just one step along the larger process for engagement. But for those that are, I'm actually seeing more use of the "News" page as the landing instead of the widgetized overview page. Part of that might be because of how mobile friendly tiles are too.