I took my parents there in September, but only spent a few days looking around.
We loved the walking tour of the old city -
http://www.freemontrealtours.com/The subway system was fantastic. Very easy to use, and very clean and safe. You might want to get an apartment close to a station.
If you cycle, well, so do a lot of people. More than I've seen in any East Coast US city. You can also cycle, run and use inline skates to cruise around the Formula 1 circuit, which I would have loved to do, but just didn't have time -
http://www.parcjeandrapeau.com/en/circuit-gilles-villeneuve-montreal/St. Laurent Blvd is the main dividing line between French (east) and English (west) speaking Montreal. Our guide said that many immigrants settle and open restaurants on this street, as they aren't always sure whether they want to be on the English or French side, so some of the best ethnic food can be found here. Also, if renting an apartment, it's something to keep in mind.
For fresh food and baked goods, there are some great farmers markets in the city. Our guide said she does most of her food shopping there.
I really like Montreal. We may go to Quebec City this summer, just for something different.
