I am a big fan of the public transportation system in Montreal. I have relied on the system countless times to get me from Point A to Point B. I've had good experiences and I've had bad experiences. Just depends on who's working the shift, as you'll read below.....
METRO: Very efficient. Good to communicate when a line is down or interrupted. Reasonably priced per trip and the map is easy to catch on to. I buy an AMT train pass that allows me access to the AMT train, the buses, and Metro. It is so convenient for me to recharge my Opus card every month. I have lost my Opus card once in the past, but I was able to get it replenished because I registered my card with the AMT/STM. I only paid for the new Opus card ($7.00), I did not have to pay for my monthly pass again. Big Bonus. I think the metros pretty clean too.
BUSES: They are generally on time and trustworthy. Many good routes exist on the MTL island. There are times, however, when a scheduled bus doesn't pass at all or the driver passes right by your stop, claiming to be full, but we can clearly see that there is still space at the back of the bus. Some of the drivers are horrendous and rude. Most of them refuse to speak English or claim they can't speak it. Others have been really friendly and approachable. It all depends on who's workin' the shift.