If you animate your aligned subs (still uncal'd) in something like CCDStack or PixInsight, then zoom right in, its quite a surprise to see what's happening with dithering. At such small scales you see a lot of the noise from the camera jump back and forth with each image. By dithering its a bit like looking through dirty glasses at an object - if you smoothly keep moving your head around you still get to create a complete composite image of what you want to see without any of the splotches permanently blacking out any of the view.
Oh heck, I'm resorting to analogies again....
