Inst. courses are good, as they give the basics. However, they should not be thought of as making someone an expert or authority on the art. Take a CPR or First Aid class. They teach basic skills. They do not teach you or prepare you for anything out of the realm in which the class was taught. In other words they're not going to prepare you to perform surgery, just like the inst. course is not going to dig deep into the art. Its skimming the surface. Follow up classes, etc., are going to be key, IMO, if you really want to be good in something.
Mike