You will hear all kinds of things about many different breeders. Weigh these things, talk to people who have bought a pup from a specific breeder, verify that any breeder you speak with tests their breeding dogs, check the health in the backgrounds of the mother and father as best as you can, and follow your heart. If someone makes you uncomfortable, remove them from your list of possibles. If someone answers your questions, treats you well, tests their dogs, you like the look of their dogs, and you don't feel their asking price is exorbidant, then keep communicating with them and see where you go from there.
You will find in this business that people will and do talk bad about another breeder just because. They may not like them on a personal level but that is not a reason to let them deter you from buying your heart puppy. Once you find the dog of your dreams, I think the best way to know if this breeder is someone you want to have a relationship with (and you will want to have a relationship with your breeder for a very long time) is to speak to former buyers and see what their experience has been like.