Out of all the times I've been to Montreal, I've had no major complaints about their transit system. Perhaps their bus system isn't as good as Ottawa, but they have great rapid transit, which Ottawa lacks. Their metro system is easy to follow if you're new to the city and the trains come often, so you're rarely waiting long. Their monthly pass is also very cheap compared to some other cities. Unfortunately, individual trips are a bit more expensive, relatively speaking.
No matter where you live in Montreal, if you're near a metro station, you'll be able to make it to the other end of the city in no time. This city has a great transit system that's well worth taking advantage of if you're visiting or a resident.
Unfortunately, I find STM staff are rarely friendly.