Montreal was a very laid back, friendly city. There are some gorgeous sites, including the jaw-dropping Basilica. For Formula 1 fans there is the chance to walk, cycle, skate or drive around the Circuit Gilles Villeneuve. During bad weather, the underground city provides welcome respite, although it is difficult to navigate round. It's worth it though, as there are some lovely shops and restaurants as well as access to galleries and theatres.
Insider Tip:Parc du Mont Royal was up a very long, steep slope past McGill University so only walk to the top if you're relatively fit! There are other entrances to the park for those who are less able to get around, and the views of Montreal from the top are worth taking in, both during the day and night.
The city does tend to shut down after summer, for example the Observation Tower was closed from the beginning of September which seemed a shame.