Fair criticism, but the subnav we had before, like the navbar, just doesn't scale. Let's less obtrusive, but hinders us in a big way. It's tough doing nav that works for everyone everywhere, but hopefully this pans out for us and folks using Bootstrap.

Edit: Also, the side nav came first, then the affix plugin. Originally I was proposing a fixed, independently-scrolling left sidebar, which we may still get to, but it felt decidedly un-Bootstrap-like for the time being.