I find that the mill marks left by the planer really need to be smoothed out or they show after finishing. The application of any kind of stain really makes them pop. While the difference isn't visible to the casual observer, if you compare two surfaces side by side where one was smoothed after power surfacing and the other wasn't, it's really obvious. Some rely on sandpaper and elbow grease. I like a few whispy thin cuts with a 4 1/2 or a little time with a cabinet scraper.