Old topic. The Roto-Zip is probably an over-rated tool...because the advertizing suggests it is a sort of "do it all" routing/cutting
tool. It isn't, but I've found it good for a couple of tasks: 1) cutting electrical box openings in sheetrock; and, 2) routing out grout
and cutting openings in tiled walls when doing plumbing repairs. You need to use the correct bits (spiral for cutting box openings
in sheetrock, and carbide for the tile work). You also need to move the tool in the correct direction (opposite to the bit rotation) to
control the tool while cutting an opening). Forget about using it for cutting plywood, metal, formica, etc., as such cuts will be sloppy
and there are better tools for those applications...e.g. jig saws,trim saws, and mini-routers (I like Bosch and Porter-Cable).