I've updated the site with a temperament description on the "Kishu Ken" page in the main navigation. I thought I'd talk a little bit about it here, too.
I first fell in love with the breed because of the description on their temperament. After meeting and interacting with the Shikoku breed a bit, this wonder with the Kishu Ken breed grew - they seemed like a "harder" dog than the Shikoku in that they seemed more willing to do what they had to do to get a job done. I liked that. I liked how their energy level was described and how they were described with strangers.
It is my opinion that the Kishu Ken's shining trait is their temperament. Sure, they are an attractive dog to look at, too, but what really sets them apart from the others is their personality and ability, in my experience--and, granted, I am certainly no expert on Japanese dogs, so this is just based on my experience.
I think, of all the Japanese breeds, the Kishu may be one of the best "first time dog owner" dogs. They are somewhat more forgiving than their cousins when it comes to handler mistakes and a little more flexible to being in new situations. They have their negative qualities, like any breed (or any person, for that matter), but I believe most people who meet one will fall in love.
They are a serious dog - but my experience has been that they do not take themselves very seriously.