I attended the "Kubotan" seminar on Saturday afternoon, and thought it was excellent. It seems to be an excellent tool for use as a "means to an end" - i.e. breaking the attackers grip, holding them in place, etc.
I had hoped to attend a grappling seminar as well. Unfortunately I could only attend on Saturday, and there were so many great instructors it was hard to choose! Hopefully I'll be able to do one next year.
Would it be possible to find out where to obtain a wooden Kubotan like the ones used in the seminar? I've seen some on the web, but mostly metal. The only wooden one I've found looked like it had a rounded end rather than the flat/blunt end.