I think the experience of countries that adopted the mixed-member proportional method of voting is telling. The two classes of members have learned to live in harmony. They have found a way to work together. I suspect that the same thing would happen in Canada.
Furthermore, the issue of political stability that you raised a moment ago is very interesting because political stability must be actually defined. In our current system, some complain that the prime minister has too much power. The fact that he would have to hold discussions before bringing forward some of his policies might not be a bad thing.