I've seen a few people who can use them decently, but it's quite rare. And the best staff fighter will probably be at about the effectiveness of middling sword-and-boarder. I don't think I've ever seen more than one in use at an event.
Functionally, it's a lot like florentine but with debateably better defense and a much, much worse offense. It also shares florentine's weakness towards archers, who will shoot you down mercilessly.
Finally, the padding requirements and striking surfaces of a staff eliminate a lot of traditional techniques. And they look silly on top of it all
.
