It works and it's cheap! I use a food processor but you can just use a regular grater for the soap. Shred 1 bar of cheap soap (I use Ivory) add 1 cup of Borax, 1 cup of baking soda, and 1 cup of Arm and Hammer Super Washing Soda. Use 1 or 2 tablespoons depending on the size of the load you're washing.
I use this for all of my family's laundry. I've also used it to soak/wash cloth diapers. My baby has really sensitive skin and it doesn't bother him at all.