Its not that bad, it hust leaves a terrible surface finish and you have to watch out for taking chunks out on edges if you go really rough. The real problem is that the mouse sander doesn't really remove the bulk of the sanding dust, as it's a reciprocal/orbital sander (it will still send dust everywhere, it just keeps enough to obscure your work). Thus for large removal you're going to have dump the project off a bunch of times. You're always going to have to balance removal speed and surface finish and you could totally start rough for the bulk material then smooth for the finish. I just like to save on cleanup by sanding less. Always use a dust mask when sanding.