Treebox,
Welcome to the forums, neighbor up 95!
To answer your question, I don't regularly use one, but will bust it out occasionally. Back when I had broken wrists, I would use the MF a lot, almost every practice. Our coach had me going 10x ~35M underwater on 1:30 or so, bulkhead to bulkhead. Built up a real strong core, strong legs, and a killer Steamline Dolphin Kick (SDK).
If you're a little unsure about it, have your team or facility buy a few (make sure they get one your size!) so you and others can test it out.
