Personally, in MY experience, I don't like the GL or the Halti. If people can use it and it works for them, I'm happy, but I can't. They don't work on high strung sensitive dogs, because to grab a dog by the muzzle is to correct it and that is totally demoralizing to a sensitive dog. Araby is like the worst puller EVER in the history of the world. I tried everything and nothing worked. I tried the GL and the Halti on her, left it on for like 10 minutes like the book said. First she flipped out, started to claw her face. When she began to draw blood I took it off. Tried again a few days later. She spun around, did backflips, everything in her power to get this thing off her face, then she compacted herself (For lack of a better word). She hunched up, tucked her tail between her legs and just stood there. It was so sad! And to top it off, it didn't stop the pulling.
The Halter collars work on the premise that if a dog's head is turned to the side, it can't go in a straight line. We used this often on horses that were refusing, or just being a PIA. You spin them around in circles and by the time you get them going straight again they forget why they were being obnoxious in the first place. The problem is, horses are a prey animal, dogs are predatory. Totally different psyches. It might work for some dogs, but I don't think that it deserves the magical pulling cure title it's been given.
Another thing I don't like about the Halter collars is that they're a crutch. If a dog pulls on a plain collar, and does fine on a Halter, the minute you take the halter off it's going to pull again. However, you can take a dog on a prong/slip and gradually move to a less severe collar, till you're working on a plain buckle collar.
Also, the next snapping thing isn't a myth. A friend of mine has a dog trainer partner (She owns a kennel), and he has had 3 dogs (And heard of others) that have snapped their necks, on standard leads. (These were people he told NOT to go to the GL, but they wanted an instant fix, so they ignored him.) Usually this happens when someone doesn't know how the product works, and can't give a proper correction.
Don't get me wrong. In some circumstances it's fine. I know Moni uses one on Tenchi if he's going to be in a situation where he could easily get distracted, just for control purposes. I use a prong on Nee for the same reason. Like I said, it's not a bad product if used on the right dog, with the right training (On the person's part) and the right situation.
Ang