Regardless of what you call this problem solving tool (fishbone diagram, cause and effect diagram, or Ishikawa diagram), it is a very useful addition to your bag of tricks.
Because a cause and effect diagram, with its classic fishbone shape, is so visual, it is an outstanding communication tool. There is also a tremendous value in using a structured, systematic, compartmentalized thinking process to evaluate the causes of a particular effect.
The cause and effect diagram is primarily used to support brainstorming sessions in which possible caused of a problem (the effect) are categorized. Each branch, the "bones", contains a grouping of similar causes.
On the shop floor, the "6 M's" are commonly used: Manpower, Materials, Methods, Mother Nature, Machines, and Measurements.