The biggest problem with zip.ca, aside from the obvious lack of streaming, is if you don't live in Ontario you're looking at long shipping times. When I was living in NJ, I had a 1 day turnaround time with Netflix but in Edmonton it was sometimes as long as a week which completely defeats the purpose of the service and the main reason why I dropped zip.
I can't even load the Canadian page they setup right now as I'm ironically currently on vacation in the US, but if they even are going to be shipping DVDs... and everything I've read so far has just talked about the streaming service, though maybe someone can correct me... I doubt that they'll have the same sorts of shipping times you get in the population centers of the US. I also wouldn't be surprised if the library available for streaming in Canada is smaller then the one in the US.