We didn't spend much time in Montreal because we arrived the day before our cruise and the weather was miserable. However the short time we spent was underground. That's where everything happens in Montreal. It's a very cosmopolitan city with lots of eateries and international cuisine which we really enjoyed.
What a gorgeous city from top to bottom. There are so many wonderful cafes and shops to see as soon as you get off the ship. We did not do any excursions but fellow passengers said the bike trip to the waterfall was excellent.
This is one of the coolest places in America. It's a fresh seaport town with so many cool little knick knack shops and eateries along the water front. Go up to Cadillac mountain or kick back and enjoy an expresso in one of the cafes. College like atmosphere.