Technically, Warmoth does not "finish" the frets - they are generally very evenly seated, but you could find a high one here and there. So if you want to approach perfection, you can level the frets. Also, the frets are not dressed, only beveled, so you'll want to do that, too - to taste, of course. Finally, the nut slots are generally cut a little shallow so folks can dial the action in their preference.
But lots of folks - yours truly included - have had success stringing up a neck right out of the box, and had no issues. It's really a matter of "pretty darn good" vs. "pretty darn amazing."