I had tried most things with my over enthusiastic German Shepherd pup with little success. At a year old, she was still pulling despite weekly training classes. My Halti arrived promptly and as noted by everyone else, my pup hated it. However, after 15 mins she gave in trying to get it off and just accepted it. She occasionally has a flip out moment when she pulls. and then jumps around like a lunatic kangaroo. I just stop, get her to sit and start again. Walking is once again a pleasure and I don;t need to grip the lead for dear life. In fact you hardly need to grip at all.
What they don;t tell you about this halti is that it is brilliant for dogs that go mental when they see another dog. Mine does and it's a nightmare. On a choke or a harness she can still pull backwards and away from me - so I'm walking by and she's trying her hardest not to whilst going nuts at another poor random dog. My shoulder is in a bad way and it's made walking miserable and anxious.
When she sees another dog and lunges forward / sideways, it immediately closes her mouth and clamps it shut. The first time this happened with the halti on she did a major flip out and looked like an untamed horse. However, she has very quickly realised that going nuts is pointless. She still spots a dog and starts the routine but for the first time, I have control. It is less scary for others, and I can walk her by other dogs with far less problems.
If you have a lead aggressive dog, try this Halti. It's in the booklet that comes with the Halti but they don;t really tell you about it before you buy. With this harness I can have nice reasonably calm walks again with the knowledge that if I meet another dog, I am in control and my pup is not. Brilliant product.