Hi @ryparken,
See this example. By making use of conditionals, elements on the page can respond to changes in the query string without reloading the page - e.g. showing/hiding groups, changing element appearance, etc. Notice the address bar URL and the text fields on the page as the buttons are clicked.
Path params are another story though. AFAIK, without a plugin, the page will reload. That was one of several motivations behind Sudsy Page. Of course, in addition to better performance and UX, there are also SEO benefits to using link elements and clean URLs.