I completed my Bachelor of Science at McMaster in Psychology, and I think it's a great school. I can't for certain explain why you haven't heard much about it for your PhD, but I'll tell you what I know. McMaster has won several research university of the year awards, so it ranks highly as a school for research. Even in the psychology department research is heavily emphasized and not clinical or counselling skills. I can't speak for your program of interest, but I know that McMaster is well known for it's medical school and the sciences, so graduate studies in life sciences, health sciences and similar programs are strong. From my experience talking to friends who studies humanities at McMaster, something that deterred them from continuing with graduate studies there was because of the specific research interests of the professors, but I'm assuming that could happen at any school.
Overall, from my experience McMaster is a great school with an inviting environment and it's highly respected among the top schools in Canada.