Our guy pulls very hard on a leash. Actually, I found it a lot easier to walk him off leash. I won't walk him around busy roads just yet though being he is 8 months old and distracted easily. We are lucky enough to have an 'off leash' dog park that has a fence around it, and lots of other dogs and distractions. With our guy 'cookie von chomp'nstein' we usually find he pays attention to us if we ignore other dogs or distractions and keep walking. If we stop when he stops, then he thinks 'Oh, its play time'. If we keep walking past the other dog and its owner, and say 'come on lets go'... he usually does. He is un-neutered and likes to sometime think he is in charge, but he more often listens to us, and comes when we ask, or at worse, when we start to get out of sight, he gets lonely and finds us. No complaints so far.
Edit: we do have some times at home he likes to take charge, and bite our feet. So we started to 'stomp walk' when he does this. He barks a bunch in confusion, then we eventually lure him to do what we want with treats. Overall, he means well and is learning what is right and wrong.