I've seen that statement on these forums a few times, too...that Charles and Camilla's visit was a great success. I don't know what the measure of success is for these visits and I don't have many memories of coverage of past royal visits to Canada, but I do remember that Charles, William and Harry visited Canada in 1998 and I thought that visit attracted more attention than this visit. Of course, that was when William was seventeen and very attractive to a lot of girls!
I know that not everyone is a supporter of Charles and Camilla to the same extent, and I know that my own feelings about them might colour my perceptions about them, but I'm trying to be very objective here--I don't think Charles and Camilla's visit went badly except for the protests in Quebec, but I don't think it was a resounding success, either. I don't think many or most Canadians cared either way, and it's not just to do with diminished support for a British head of state, although that's part of it: but people are not hugely enthusiastic about Charles. More Canadians support the Queen than they do Charles. I don't think the visit made most Canadians more interested in or more supportive of the monarchy, so if that's the basis for a successful royal visit, I don't think Charles and Camilla's visit was one. On the other hand, I don't think the visit worsened anyone's perceptions of the monarchy either, so if that qualifies as success, then I'd say the visit did succeed.