The stm is a great way to get around Montreal. Fares are reasonable and have many options for locals and tourists.
Fares can be bought at opus machines in metro stations or some retailers such as jean coutou or pharmaprix.
One thing I dislike about Stm is their front line staff... Don't get me wrong there are some great staff at the stm but the majority of them just stink! I remember one time I was on the route 51 bus and asked the driver nicely for directions in my broken french, the lady who was driving the bus asked me "do I speak French?" I replied "a little" and she says "well I do not speak english" and gave me a disgusted stare and started muttering something in French... I was like WTF???
I would of gave Stm 4 stars if the staff provided better customer service.