My keyboard had gotten to the point it actually offended me to type on it. After a semi-thorough cleaning with antiseptics, chisels, sandpaper, and various brushes, it has some of its original color showing through again, and no longer appears to be a science experiment gone wrong. I also found enough cat hair to make Miss Kitty a new wig.
For a quick test, turn your keyboard upside down and shake it a bit. If your desk is obscured with debris, consider your keyboard a 5 on the scale. Minor speckles score lower (though bugs of any sort propel you off the scale).