What do you think of Feingold’s diet for hyperactive children?

What do you think of Feingold's diet for hyperactive children? My friend told me to take my son off a lot of foods. The Feingold diet for hyperkinetic children is based on removing all foods with sugar, preservatives, color dyes and salicylates from a child's diet. Specific foods are omitted. Hyperactive children vary from three to...