What kind of halter are you talking about?
I wouldn't bash the gentle leader so severely, its almost impossible to get off when fitted properly and gives you lots of control over a reactive dog. I've used it on three dogs for training and not once has it come near to coming off.
Maybe it doesn't work for you and your dog but it works for plenty of people, including myself. Someone on the forums mentioned that they thought a Halti was better (maybe that was you), which didn't work for me or two of my shelties but that doesn't mean that its not good, it just means that it works better for other people and different dogs.
With a reactive dog its important that the leash connects under the chin and not at the back of the head, for maximum control for dogs with reactivity issues.
Toby reacts at people, dogs, trucks, buses and anything he sees and hears that he thinks is scary. He's both noise and movement sensitive, I don't know what I'd do without Toby's gentle leader, which he may need for life.
Do your guys still pull with the GL. Ryder still pulls with it on. Probably not as bad as with out it..but he still pulls. He hates it!! he runs and hides every time he sees it.

I was always hoping to join the Agility club but seeing his awful reaction in class I am now thinking that is out of the question.
) The technique Tracy showed in the video really does work. Shelties are so smart that they will figure it out. Maia would go crazy when she would see dogs run agility and she was just standing watching. This method really did help with that.
)