Hi there,
I wanted to share my experience with you, since I had the same issue last week and after reading comment after comment, I decided to just gather up some courage and go and see what happens!
I'm not from a Visa-exempt country; in fact, Canada is very strict on the citizens of my country. I had my Immigrant Visa on my passport which was issued to me in order for me to complete my PR status. It was scratched up and there was a thin cut on it! And when I went on my trip, I asked people at home to mail me my PR card when it arrives but it took longer than the time stated, so when it was time for me to return to Canada, all I had was my Confirmation of PR and that scratched Visa.
The airline examined the visa and gave me my boarding pass, and in the connecting city, I passed border control with suspicious looks, but she still let me pass after scanning the visa and noticing it is not fake. I passed 3 passport control with that visa and no one questioned anything.
At Pearson, I told the officer that my card didn't arrive, but I still have my visa which hasn't yet expired, and my COPR. She was very nice and sent me to the second screening for visitors. The second officer was also nice. She told me I was lucky the airline let me in, but at our border, they're pretty lenient. She also said next time it won't be like this and I need to remember it. I just said, OK, sure, fine, thanks.... ;D and I entered Canada! I guess I was lucky, but as long as you can board the airplane and can pass passport control, I don't think the border would give you that much of a hard time.
Also, I had some other documents ready in case they needed to see them - my partner's passport photocopy, my lease, my income tax papers, etc. to prove I live here.