Personally I dont like them, I would always rather work through issues without gadgets, plus I find them very hard to ride in.
My OH uses them on his mare occasionally and I must admit they help to get her sitting behind a bit as she does tend to run through her forehand but they are definetly not a long term fix.
Im indifferent really i would never use them myself unless under instruction as i have never used them before and imo like anything can be awefull in the wrong hands. But in the right hands im sure they make a valuable training aid like anything.
To be honest i think people need to stop worrying if what "jane down the yard" thinks and just do/use what is best for their horses, and if thats draw reins then so be it.
I used to use them on my thoroughbred. They worked really well for him, used with a kind hand. I did not use them tight though only tight enough so that they came into effect when he put his head too high. Although now i have more experience of riding horses into a correct outline, i would only now use them in extreme circumstances.
I've used them once, under supervision of a very experienced person. Simply as horse was completely taking the p*ss, and said person instructed me to fit them and use them exactly how he said. Horse quickly figured out what was what, behaved, took them off and all was good. He instructed me not to use them when he was not around at the time, which was probably good as I wasn't half as experienced then even though it wasn't too long ago! They served a purpose though.
I would now be happy to use them of my own accord, I think they have a time and place, and must not be abused or over used. However, I haven't found a need for them yet!
Don't particular like them, feel they do more harm than good, often cover up underlying problems and is a quick fix rather than going back to basics to sort out the issue.
Plus think they can lead to a lot of hock problems if overused and used incorrectly especially if used on an under developed horse making it sit on it's back end when it may not phsyicallyl be able to do and thus putting additional strain onto the hocks.