A common thread I've seen in the reviews I've read about most Montreal restaurants is that food quality may vary, but service is almost universally poor. I'm happy to report that I got both great food and good service at Dunns.
Based on what fellow Yelpers recommended, I tried the smoked meat sandwich and poutine. The sandwich was delicious. The sides were top-notch. The poutine was among the best I've had in Montreal. The portions were big and the quality didn't suffer for it.
The service was prompt, helpful, and friendly.
Beginning to end, a good experience.