Depends on what you mean by perfect. its very precise, but I'm sure if you examined the surface with an electron microscope you'd still see imperfections.

Edit: was incorrect about what I said below. Leaving it for posterity

It's important to remember that the final surface - the one that actually reflects photons - is created chemically by releasing a gas inside a vacuum that very evenly coats the surface with reflective metal atoms. I'd wager that process fills in the ~last nanometers~ or so of imperfections. Or at least averages them out enough to not affect the optical performance.