I enjoy attending seminars with good instructors. My personal take is that they are not a good venue to learn any sort of specific techniques or art. However, I have never failed to learn something about budo, or the arts, or movement, or about life. Often more learning can be had by hanging out with everyone at the bar after a day of training than can be had at the actual seminar itself. I've yet to attend a seminar or competition that I felt was not worth the effort.
"Always keep the sharp side and the pointy end between you and your opponent"