I guess the point I'm getting at is that the virtual DOM's speed is really just the answer to the question "But isn't re-rendering the whole world over and over really slow?" Which is the first thing anyone deeply familiar with web UIs would ask.

It's the solution to a problem that arises when you move to this programming model. It's the programming model that's the real advantage. The virtual DOM's speed is worth mentioning because it remedies what would otherwise make React completely impractical in the real world.