I have one for my horses. It's another one of those things that is a great tool to have, but it can't be relied on to do all the work for you. You still need to be able to time your own releases perfectly otherwise the whole purpose of it is lost.
We have dually halter as well. I used it once, but it just didn't seem much different. It just applies different pressure on the nose. I have a rope halter in my tack room, and I'd love to use it, but I have no clue how to. I've watched videos and what not, and it just seems so freakin' confusing. Anyone have any tips on how to tie it and all that good stuff??