The cool part is that Rendr builds a backbone hierarchy around server generated HTML, attaching the rich interactions after the page has been displayed. Although, if the user starts to interact before that view hierarchy has been constructed, for example by clicking on links, the behavior won't be "rich". (However that would require some fast clicking!)
The author (spikebrehm) speaking here - that's a good observation! It's possible that the user will click on a link before the JS finishes downloading. Luckily, we've taken care to use real URLs for all links, and our pages render fully on the server as well, so if they click before the Backbone views initialize, they will fall through to the server. Not the fastest experience, but still fine at the end of the day.
