I can tell you that my experience has been largely good with my dog and her flock. She is mixed breed (German Shepherd Dog and Boxer we think). When we first got our chicks she was only about 6 months old. We lost one bird- my husband and I disagree about what happened, but it's possible that she played too rough-we didn't see it. However, since then, (it's been 2 years), she hasn't hurt any birds. In fact, she will break up cockfights when they break out- which helps keep the peace. The one thing she does like to do is occasionally run past the flock, startling the ladies. Whether this is intentional or incidental, I don't know for sure, but I think she gets a kick out of it. But she knows that "No chickens" means to back off. And, at this point, the chickens are used to her antics.
I think it's probably smart to choose your dog breed carefully. It seems like a shepherd would be a good choice. Also, look for articles on introducing dogs to chickens. Be patient and don't leave them alone until you are pretty sure the dog isn't a risk. Good luck!