I was often tempted to buy one of these, but always held off. On one of my Yahoo groups, an old sharpening trick was posted and I've had tremendous success with it - with scissors, pinking shears & rotary cutters.
Take a sheet of aluminum foil, fold it over 2 or 3 times and cut with scissors or rotary cutter as many times as needed to sharpen. IT REALLY WORKS!
Terry in N :D