According to the Bushido specials descriptions I've read there is no effect on the move. You need 50 Bushido to be able to use the weapons that have that special however.
Actually it can be pretty effective at times. No-dachi is what I use that has that weapon special on it. Hard to find a good one unless you can make them yourself.
If you are riding on a mount you can stun and damage your opponent.
However if you are on foot, it works the same as any other common weapon used for dismounting: lance, magic wand, etc.
I guess you can also damage the rider's mount if you are on foot and say they're a tamer, but I've never had the opportunity to do that.
