I've seen some KA Koncepts.... and I may have sailed one once, but I really have no experience with them.
I don't comment, good or bad, on things I have no experience with.
The sails I've seen seem to have pretty good build quality, and the guys sailing them seem to like them.
They are probably very good sails, but I don't see any results that indicate they are remarkably faster than other speed slalom sails.
Hope this helps,