Depends on what you are looking to gain by taking the course.
If the ASA Certification Curriculum is important to you then Yes, you will need this as a pre-req to most of the courses. It is also a good way to meet people in your area that like to sail. Even an experienced sailor will probably pick up a couple of pointers from the course, but the written test is primarially vocabulary questions and matching (Leech/Luff/Foot, Cringle/Head/Clew, Running/Standing rigging, Tiller/Telltale Bow/Transom, Port/Starboard, etc....)
If you have sailing experience, and simply want to charter, it is not needed.