The kubotan is a great addition to a person's defensive tool box. I've found they really enhance basic defensive skills. You don't have to do anything really fancy but you do need to understand the basics and to properly use one, or to defend youself in any mannor, you really should get some professional training. And they are perishable skills so you have to practice some.
I'm not talking years and year here like it might take to master a martial art, but rather a couple of key concepts and half a dozen techniques. Any person who is serious about thier personal safety should get some intellegent, professional training that transitions to both edged and blunt weapons. Kubotans fit in quite nicely and are very effective when the techniques are properly applied.